Like giant pieces of fabric woven into the economy, the American textile and clothing industries spread far and wide, into nearly every state of the Union.

Cotton farmers and ginners; textile plants spinning miles of natural and man-made fibers into fabric; factories turning out clothing and home furnishings as well as fabrics for automobile tires, electronic circuit boards and countless other products -- all are part of a $45 billion industry that accounts for one of every eight manufacturing jobs in the United States.

From that vast constituency has come a cry of anguish and protest that is helping to change the course of American trade policy.

"We're in a war, and we're going to fight like hell. We're not going to give up," said Ellison S. McKissick Jr., president of the American Textile Manufacturing Institute.

The American textile industry is reeling under a tide of imports that threatens it with ruin.

Shipments of fabrics and clothes from abroad doubled between 1976 and 1984, with most of the increase coming in the past two years. Imports took nearly 23 percent of U.S. textile market last year, double the 1979 level, and imported clothes captured an even larger share -- 33 percent, compared with 22 percent in 1979.

Nearly 50 textile plants have been closed this year and at least 20 others have imposed permanent layoffs. More than 10,000 textile workers have been laid off so far this year and the industry's unemployment rate stands at 13 percent, compared with a national rate of 7 percent.

The industry has won wide support in Congress for legislation that would drastically limit this huge surge of imports.

The textile bill, backed by executives and labor representatives of both the textile and apparel industries, has become the first major test in a political firestorm over America's declining position in world trade. With nearly 300 pieces of trade legislation pending in Congress, the passage of the textile bill could spark a stampede by various constituent groups to win approval of single-issue trade measures, many lawmakers say.

This in turn could touch off a trade war, with unforeseeable consequences for the world economy.

President Reagan has vowed to veto the textile bill -- passed by the House last Thursday, 262 to 159 -- while promising much tougher action against unfair trade by foreign countries.

"If our legislative effort fails and our government is determined to continue the same policies that it has adopted over the last four years, you're going to see a demise of our industry," warned McKissick of the ATMI, the industry's Washington-based trade group.

The problems of the U.S. textile industry epitomize America's trade quandary.

In the industry's eyes, the problem is unfair trade -- a boom in imports since 1980 that violates an international agreement signed by the United States and other major textile producers. The industry is penalized as well by economic factors beyond its control -- particularly low wages abroad and the high value of the dollar, which effectively cuts import prices while boosting prices of American exports.

Critics of the textile bill call it the worst form of protectionist legislation. The House version would cut textile imports by up to 40 percent, denying American consumers access to foreign clothes and cloth that are often much cheaper than competing American goods. To save jobs of textile and apparel workers, the legislation would prop up non-competitive parts of the industry -- a wasteful, inefficient bargain for consumers, say the critics, who are led by the nation's retail industry.

Is the issue fair trade or protectionism? Would imports lead to retaliation by foreign countries or force open the door to a fairer, more open trading environment? Is this the first step toward a raising of barriers to trade around the world?

Those are crucial questions on which the current debate on textile trade legislation will turn.

There is no one factor that is clearly responsible for the problems of the U.S. textile and apparel industries, and thus no one solution to them. But scholars, economists, government trade specialists and industry officials point to these in particular:

*Imports produced by low-cost labor. The huge disparity in wages paid here and abroad gives a distinct cost advantage to foreign producers, according to industry and government officials. Wages received by apparel workers in Taiwan, Hong Kong, Korea and China, for example, average one-fifth to one-tenth of those paid to their counterparts in the United States, industry and government studies show. U.S. textile workers are paid between $6 and $8 an hour.

Although the dramatic rise in imports has been attributed mainly to increased production in the Far East, the United States is also being targeted producers in an increasing number of developing countries in other parts of the world where labor costs are low.

*Subsidies by foreign governments to their manufacturers: Commerce Department officials here say that subsidies pose a major problem and that the practice is fairly sophisticated. It is "almost impossible under our current law to prove subsidy activities in centrally planned economies" where governments are integrally involved in manufacturing, says Walter A. Lenahan, deputy assistant secretary of commerce for textile trade.

*Protectionism abroad: While the textile trade bill pending in Congress is being widely attacked as a protectionist measure, American-made products are systematically barred by the governments of many foreign competitors.

*Fraud. U.S. Customs officials say fraud compounds the textile import problem. Practices range from false labeling to smuggling to transshipment of products from one country to another to circumvent quotas.

*The dollar. The huge increase in textile imports, which have grown by 20 percent per year since 1980, corresponds with the soaring increase in the value of the dollar. Textile imports actually declined between 1972 and 1980, when the dollar's value was relatively low.

But attributing the imports problem mainly to the dollar misses the mark, say textile industry leaders. The same factors -- protectionism, cheap labor, subsidized foreign production, fraud and expansionist trade policies of nations with central economies -- were at work before the rise in the dollar and will be when it drops, these officials say. An expanding number of less-developed countries capable of supplying textiles has sharpened the competition for the U.S. market, Commerce Department studies show.

"One of the basic problems of our domestic textile industry is that it is basically excluded from major markets where I think they could be competitive," Lenahan noted. "Our ability to ship to Korea is almost nil, despite the fact that Korea ships over $1 billion a year in textiles and apparel, plus our ability to ship to Taiwan as well, even though they ship $2 billion in textiles. The Philippines, Indonesia, Thailand, India, Pakistan -- major supplier after major supplier effectively excludes us from their markets.

"If we could have an equal footing in those markets I think we could compete both domestically and internationally."

But textile industry officials express doubts about their competitiveness both here and abroad.

"You simply can't compete with a government that is absolutely dedicated to keeping its people working for 16 to 18 cents an hour," complained James H. Martin Jr., vice chairman of Ti-Caro Inc., a Gastonia, N.C., textile company. "We've seen the pattern in the destruction of American jobs and we're not just whistling in the graveyard. If this thing continues, we'll have segments of this industry that will be totally, absolutely forever gone."

"You can't entirely overcome the wage disadvantage ," Lenahan acknowledged. "I don't think anyone should fool themselves. At the capital-intensive end of the industry, I can see the wage differential being overcome. It gets more difficult in apparel because of labor intensity."

The import explosion over the past decade has been fueled primarily by the so-called Big Five -- Hong Kong, Taiwan, Korea, Japan and China. Average annual growth in textiles and apparel from Hong Kong and Japan declined slightly during the period but import trends tracked by international trade specialists in the Commerce Department show a rapid growth in volume shipped by Taiwan and Korea. China also became a major supplier of textiles and apparel to this country, increasing its shipments from from 1.7 million square yard equivalents in 1976, to 268 million SYE in 1984.

While the United States has absorbed an estimated 95 percent of the increase in world exports from developing countries, the growth rate for the total U.S. apparel market over the past 10 years has been only 1 percent. Thus while textile shipments have been a key source economic growth for these countries, the results have been disastrous for domestic American producers.

In the meantime, imports from the European Community -- an economic union of 10 nations -- increased at an average annual rate almost 7 percent faster than those from Hong Kong. Taken together, the EC-10 would constitute the second-largest supplier -- after Taiwan -- of textile products to the United States, according to the Commerce Department.

Ostensibly, the textile trade bill would ensure an orderly flow of imports by establishing global quotas. Supporters of the bill say it is intended to strengthen existing provisions of the Multi-Fiber Arrangement (MFA), which went into effect in 1974 and which was extended in 1981 for five more years.

The MFA, to which the United States and most major textile-producing countries are parties, provides for the orderly growth in textile and apparel imports through bilateral agreements or unilateral controls. But it hasn't worked that way.

The textile industry is comprised mostly of family owned or small privately controlled companies. Unable to compete against the flood of imports, several have either been forced to declare bankruptcy or are on the brink of collapse.

Although the industry is generally thought to be concentrated mainly in the South, it is, perhaps, more a national industry than most major manufacturing sectors. Textile plants are located in at least 42 states. Forty-five states have apparel plants and 48 produce raw products such as cotton and wool or man-made fibers.

The industry generates a gross national product in excess of $48 billion, compared with $51 billion for the auto industry, $43.1 billion for primary metals and $31.6 billion for petroleum refining.

The import damage extends beyond the smaller companies. Textile manufacturing giants are also at risk. At Milliken & Co., the industry's third-largest manufacturer, for example, employment is down 25 percent after the company was forced to close 11 of its plants in the Carolinas and Georgia the past couple of years.

J. P. Stevens, meanwhile, in an action stemming directly from the impact of imports, has decided to sell off its finished apparel fabrics business. Chairman Whitney Stevens said the company will concentrate on its home furnishings business and industrial products to ensure a better return on the company's investment.

Stevens, one of only a few publicly held textile manufacturing companies, attributed a $4.8 million loss in the second quarter to a major restructuring, which included the closings of three plants. The closings led to the layoff of nearly 1,100 Stevens workers, bringing the total to more than 7,000 since 1980. The big New York-based manufacturer has closed 17 plants since 1980, and plans to close at least two more by the end of this year.

"There was a time when you used to go to a managers' meeting to see how high your profits were," mused Paul J. Poston, a Stevens plant manager in Piedmont, S.C. "Now you go to count your losses. It's gotten to the point where managers call the meetings the blood bank now." CAPTION: Pictures 1 and 2, Worker Harold Taylor examines Cotton at a mill in Peidmont, S.C., the $45 billion testile industry accounts for one of every eight manufacturing jobs in the U.S.; Ellison S. McKissick, president of the American Textile Manufacturing Institute, at a southern mill.