A Greyhound bus, its destination window reading simply "America," pulls over for the inevitable pit stop at the inevitable McDonald's, whose golden arches poise like a garish plastic gateway outside the entrance of this magnificent national park.

The bus disgorges a full load of Japanese tourists, waving wads of dollars.

Ronald McDonald's teen-aged waitresses move a step slower for the foreigners than they do for neighboring Californians.

Not long ago, foreign tourists were as rare in the isolated western United States as a nun in Las Vegas. But this year, 80 percent of the arriving passengers at the local airport are from overseas. Fully one-fourth of the parks' visitors are foreigners.

In this recession summer of 1980, as Americans struggle to adjust their family vacations to $1.25-a-gallon gasoline and $50 motel rooms, the foreign tourists are everywhere, finding a changed America -- a land of cheap milk and low-cost honey.

Converted yen were outstretching the one-proud dollar at the Big Mac counter; the mighty German mark was going further than the embattled buck at the hot dog stands inside Grand Canyon National Park.

At times, the deluge of foreigners, spending dollars the way Americans once fluttered lire and shillings in Europe, seemed to frustrate isolationist westerners almost as much as what they see as other symbols of American weakness -- U.S. hostages in Iran, imperious oil sheiks and Soviets marching unimpeded into Afghanistan. Play Cowboys and Iranians" bumper sticker, antagonistically kicks up a cloud of gravel and dust as it races past a rented California Buick with a sign pleading, "We're French -- Help us Discover America."

In Nevada casinos, steely-eyed pit bosses look with chauvinistic disdain at Arabs who blithely push stacks of $100 black chips across the same gambling tables at which Americans are betting $5 rerds and risking it all with $25 greens.

It is as if the American Century, fueled by a once-mighty dollar that reigned supreme throughout the world, is stalling out not only overseas but right here in the limitless expanse of the West as well.

Not only the hosts are sensing the change and, occasionally, the frustration.

Gunter Pomberger dangled bronzed legs over a rocky cleft named Yavusai Point, aiming frazzled Adidas into the Grand Canyon, toward rainbow-colored wonders called Tonto Platform and Shiva Temple and the muddy Colorado River almost a mile below.

From the 23-year-old Austrian student's vantage point, America stretched out forever in a panorama of power, strength and endless resources.

It was an odd place for Pomberger to see an end to Pax Americana. As a child -- before the American spending orgy in Vietnam, before the Organization of Petroleum Exporting Countries drained off American billions, Pomberger had watched Yankee tourists parade like royalty through the streets of his native Vienna.

Now he stared down into the canyon and saw a wry paradox as he watched American helicopters, reminding him of those that failed an Iranian crossing, swoop tourists past Shiva Temple at $40 a head.

The paradox was made even more wry by the knowledge that the shillings he had brought from Vienna could buy that helicopter ride less dearly than a New York student's dollars.

"You are wasting it all, your strength and your resources," Pomberger said in a simple critique that covered all kinds of waste, from rusty tanks left behind in Vietnam to rusting automobiles he had seen discarded like beer cans along the western roads he has traveled for three weeks.

"You think your wealth will go on forever, like your rivers, but no one can afford to discard automobiles."

Pomberger is not a harsh critic, more puzzled than hostile about the odd American psyche that finds both weapons and automobiles disposable.

The Austrian doesn't expect to discover America in the month he will spend here. He is much more concerned about Americans discovering themselves, because Americans "have more control over my life, than you seem to understand."

"You are in a crisis, both a government crisis and a personal crisis that does not help me or my country," he said."You do not understand who we are and you do not know who you are."

His 22-year-old traveling companion, Birgrit Baumann of Oldenburg, Germany, is astounded when Americans her age don't know about the division of East and West Germany. She is amazed when they hear that Gunter is from Austria and they want him to sing "Waltzing Matilda" because they think that's what is sung in his homeland, Australia.

But Birgrit is even more perplexed traveling through America during a presidential election that "you treat as a circus, all balloons and dancing, with a president who goes to Mexico and speaks of Montezuma's revenge and an actor who can't remember the name of the leader of my country."

Birgrit is a draftsman, studying to be an architect, and she likes the Americans she has met, but she doesn't like the mood here at the beginning of the 1980s. And she says flatly that she fears the United States as much as she fears the Soviets.

"The Russians are bullies," the German woman said. "But why do you let them bully you? Why do you let them bully you into making bigger and bigger weapons that someday you will have to use? I am afraid that you will start the war because you seem so afraid.

"Everything you do is too big. Our response to the Russians is too big, your cars are too big, your houses are too big. As long as you keep building things too big, and as long as you let the Russians keep you afraid, it is my mark that will really get bigger and your dollar that will get smaller."

Pomberger listened, glanced out across the vastness of the Grand Canyon, and offered the opinion that "a lot of Americans think more about what they want to have than what they want to be. Americans will be happier if they think more about what to be."

An old Japanese man, Fujimar Kita of Yokohama, stood near the edge of the conversation and finally interrupted.

"We like it that you are the fortress for our country," Kita said. "You build the weapons while we build the cameras and the autos and the televisions."

Kita was making his first visit to the United States at age 67. He had seen the skyscrapers of New York, the powerful government sprawl of Washington and the wide open spaces of the West.

"But I will tell you," the old Japanese said,"about the happiest people I have seen in America. They are the Dutch, the how do you say, the Amish, in Pennsylvania. They have no cars, neither yours nor ours."

Pomberger grinned. He looked again into the endless canyon, where multicolored strata of rock measure incomprehensible time, two billion years of the earth's history exposed to his gaze, all of man's history no more than a boulder or so, the American Century no more than a pebble.

"You want everything American to be as big as your canyon," Pomberger said. "You need time to find who you are and what you are to be."

The next morning, after Pomberger moved on, a three-year-old American girl rushed into the Canyon Edge Dining Room for breakfast in the old Santa Fe Railroad hotel, the El Tovar. She ran to the window for her first look at her country's greatest natural wonder, surely the grandest and biggest thing she had ever seen.

"Is that America?" she excitedly asked her father. Her father nodded, then continued with his bacon and eggs, which he thought were a bit high-priced for his American dollars in the summer of 1980.