In the aftermath of the Falkland Islands conflict, Venezuela's leaders have begun what they describe as a painful and soul-searching reappraisal of their relationship with the United States that has already sharply reduced their involvement in U.S. initiatives in the region.

The reevaluation by Venezuela, considered one of Latin America's few stable democracies and a key U.S. ally, reflects a similar process of reflection on issues of hemispheric security and unity that officials here are encouraging throughout the continent.

It is spurred in large part by lingering bitterness over Washington's staunch support for Britain in the South Atlantic war, in which Venezuela was a major backer of Argentina. Most troubling, said Venezuelan officials, was the change of the Reagan administration from mediator to adversary once negotiations over the islands broke down.

"What was really upsetting," said one government official who asked not to be identified, "was the idea that the U.S. would not support us if we were attacked from abroad--that the security net we had always counted on had holes."

Venezuelan President Luis Herrera Campins, who strongly criticized U.S. policy during the conflict, put the matter even more bluntly at a press conference last week: "The United States has to make a great effort to understand Latin America--and not make so many mistakes."

While Venezuelan officials say that the Falklands crisis will not substantially change the strong economic and political ties that have bound their 24-year-old democracy to the United States, they have pursued a series of foreign policy changes that run somewhat contrary to stated U.S. policies.

In the last several weeks, Herrera has proposed joint action by Latin American leaders to restructure their relations with the United States and strengthen their internal ties, possibly through the creation of a new regional political organization.

At the same time, Herrera has made a number of significant shifts in Venezuela's foreign policy, moving toward membership in the nonaligned nations movement and the strengthening of relations with Cuba and Nicaragua, while markedly cooling Venezuelan support for the U.S.-backed government in El Salvador.

Venezuelan leaders also warn that without concrete action by the United States to repair Latin American ties--and help arrange a peaceful solution to Argentina's continuing claim to the Falklands--governments throughout the continent may begin a long-term shift away from Washington.

"It worries me that perhaps people in the United States do not have a clear perception of what is happening here," said Marcial Perez Chiriboga, Venezuela's ambassador in Washington, in an interview here last week. "I have heard people say that everything will be business as usual, without evaluating the feelings in Latin America. But the fallout of the crisis will depend to a large degree on the attitude that is taken by the U.S."

Despite its relatively small size and population of 14 million, Venezuela has frequently played a key role in Latin American politics in the last two decades because of its wealth as an oil exporter, its strategic location on the northern coast of South America, and its stable civilian government.

Venezuela also has enjoyed particularly close ties to the United States. U.S. imports form the largest part of Venezuela's oil trade, and U.S. firms hold 30 percent of Venezuela's internal consumer market. Television here is dominated by advertisements for U.S. products ranging from cars to shampoo.

Yet despite this country's vocal criticism of the region's military dictatorships, Venezuela was the leading ally of the Argentine junta's failed seizure of the Falklands. The government backed up its rhetoric with supplies of arms and spare parts for warplanes.

Venezuelans say their attitude is explained by a variety of factors, ranging from internal politics to strategic considerations and a popular tradition of Latin solidarity that led to the uncritical acceptance of Argentina's cause as a kind of symbol.

A major factor in the popular support for Argentina--measured at 96 percent by a Gallup Poll during the conflict--is Venezuela's own territorial dispute with neighboring Guyana, a former British colony. Venezuelans blame Britain for seizing 150,000 square miles of Venezuelan territory in the 19th century, and still recall that a British war fleet was posted off the Venezuelan coast to enforce the claim.

"We accept Argentina's case because we have been bitten off ourselves by the British Empire," said Jorge Olivarria, publisher of a Venezuelan magazine that ran a caricature of Margaret Thatcher as Hitler during the crisis.

Within days of the Argentine invasion, Venezuelan newspapers and television were stridently supporting the move and attacking British "colonialism." There were street demonstrations against both the United States and Britain, and television stations promoted solidarity blackouts of house lights. "It was a grand intoxication," said Bayardo Sardi.

Argentina's crushing defeat was a major disappointment here, but more sobering, officials say, was the perceived failing of the United States to honor its defense commitment to Latin America. "The main consequence has been a maturation in the sense that we should complete our own objectives without waiting for the help of the industrial nations and the United States," said Juan Jose Monsant, foreign policy director of Herrera's Christian Democratic Party.

Most concretely, Venezuela has moved in the past month to solidify its ties with key Latin American nations, including Cuba. After withdrawing its ambassador from Havana in early 1980, Herrera's government is expected to open political negotiations with the Cubans to repair relations in the coming months.

Herrera also announced earlier this month that Venezuela would "study" full membership in the Cuban-led Nonaligned Movement, a key organization of Third World nations that often has attacked the United States.

In another symbolic move, Herrera was the only foreign president to attend last week's anniversary celebration of the Nicaraguan revolution. There he delivered a strong address that repeated his "profound disagreement" with the United States for "putting itself at the side of the imperialist and colonialist aggressors" in the Falklands.

At the same time, Herrera has sharply cooled his support for El Salvador following Jose Napoleon Duarte's ouster as president.

Both Venezuelan officials and diplomats here say the shifts were not solely the result of the Falklands crisis. But, said one diplomat, the Falklands "opened the door . . . . There was a feeling that Venezuela was too close to the United States and they can now prove to the world that they are not in anyone's hip pocket."

Beyond these changes, Herrera has proposed a meeting of Latin foreign ministers in Panama to discuss U.S. relations and the future of the Organization of American States. Venezuelan officials also have called for the expansion of organizations such as the Andean Pact and the Caracas-based Latin American Economic System.

But with emotions quickly cooling following Argentina's defeat, many Venezuelans doubt that the efforts for change will soon bring about any dramatic results.

Venezuelan officials also unanimously predict that the most extreme moves suggested during the crisis--such as the exclusion of the United States from the OAS--will never come about. "The problem is not as simple as excluding the United States from organizations," said Simon Alberto Consalvi, a former foreign minister.

"We believe that friendship with the United States is indispensable. These relations will be conventional, but the difference will be they will be carried out having learned from the experiences we have had. We know now they don't depend only on good will."