OUR NEW PRESIDENT has displayed such extraordinary political verve, not to mention eyes-open smartness, that it leads me to indulge in unreal expectations of him. He has conquered Congress and baffled liberals and artfully bruised the nut fringes of his own constituency. Now will Ronald Reagan also have the nerve and wisdom to tell our dear allies, the Europeans and Japanese, that "Uncle Sucker" is dead?

I expect not. When the president goes to Ottawa next week to meet with the political leaders of the Western alliance, I assume that he, like his many predecessors in the White House, will mumble the reassuring euphemisms which the allies love to hear. America promises to be strong and steadfast. To spend more of its great treasure on defending freedom in their behalf. To bow and scrape graciously when our allies complain. In short, America promises to continue the neurotic, expensive arrangement by which U.S. citizens subsidize our toughest economic competitors. In return, the allies promise to kick us in the shins whenever they see an opening.

Let me fantasize for a moment on what Reagan might instead tell the assembled leaders:

"I have come to Ottawa, my friends, to deliver a sobering message from the American people: Uncle Sucker is dead. Americans have always been willing to help the weak and defenseless but it makes our blood boil when someone tries to take advantage of our generous nature. A generation ago, it made sense to keep 10 American divisions in Europe when your nations were weak and divided. Now it makes sense to start bringing the troops home. For many years, the United States was glad to provide military security for Japan and defend world sea lanes so it could build its trade. Now Japan is prosperous beyond anyone's dreams and it must start paying its fair share of the burdens.

"Our allies, I know, will accuse us of threatening the alliance, of acting precipitously without adequate consultation. But our allies must understand: I have just asked the American public to accept major reductions in the domestic social programs which insure their well-being in order to buy more tanks, airplanes, bombs and rockets for your defense. Now a growing number of Americans are beginning to wonder why Europe and Japan refuse to do the same. If the American public ever wakes up to the fact that it's being conned -- look out."

Okay, I said this was fantasy. President Reagan, committed to his early '60s version of global realities, is not likely to perceive that the Western alliance is a grand hoax waiting to be exposed, that it's time to force a new relationship. He seems too deep into simple-minded Cold War rhetoric to grasp that the world has changed and the old rhetoric is wrong.

Still, this issue is one of the great political opportunities of our time. If Democrats had the wit and nerve (lucky for Reagan, Democrats seem short of both), they would pick up the subject of our feckless allies and exploit it to Reagan's embarassment. I could write their speeches too and I guarantee hearty applause from common-sense voters.

"Why should America's elderly give up Social Security benefits so the West Germans can stay fat and happy and muscle out American products in world trade? Everyone knows West Germany is flush. Why do its citizens spend only $378 per capita on defense while Americans each contribute $527? Why did Herr Schmidt break his promise to raise defense spending? Why does Reagan let him get away with it?"

Or: "While Ronald Reagan rails against government subsides for the poor, why doesn't he ever mention the government's much bigger subsidy to our rich ally, Japan? After all, which is more painful: giving food stamps to Americans or giving a free lunch to Nippon? Japan spent $11 billion on defense last year. Less than 1 percent of its gross national product. Can you believe it? When Gen. Haig gently suggested that the Japanese ought to spend more, the Japanese bluntly said, no, thanks, Al. Meanwhile, Americans are going to increase defense spending by more than 100 percent in the next five years -- headed toward $350 billion a year. Can you believe it?"

Or: "While he's in Canada, the president ought to have a little attitude talk with our friend and neighbor, Monsieur Trudeau.The Canadians are perhaps the biggest freeloaders of all. They spend less because they know we will spend more. Last year Canada devoted 1.8 percent of its GNP to defense -- we devoted 5.5 percent of ours. And that gap is going to get much wider in the coming years.

"And don't leave out the British and the French. Britain's 'Iron Lady' is planning to cut back her navy and leave more of the job to us. The French always go their own way, of course, but they are still riding on our backs. It's time for our allies to grow and share the burdens of leadership. That means money. Americans got fed up with foreign aid to the poor nations of the world, which is a trifle compared to the military subsidy to the strong nations. Sooner or later, Americans will wise up."

Do I sound like a yahoo? The "responsible opinion" which guides American foreign policy has always treated this like a forbidden subject. Only demagogues or subersives would make such irresponsible proposals. Whenever I froth on the subject of the 300,000 U.S. troops still stationed in Europe, a colleague reminds me that I grew up in the Middle West and hints that I am still infected by midwestern isolationism.He thinks that is an insult.

Well, it's true but I'm not insulted. I grew up in Ohio when the opinion leader was Sen. Robert A. Taft, where insular citizens of the heartland were probably excessively proud and provincial but could also look at Europe, especially England, without being overawed. Isolationism was wrong, no question, but it also expressed valuabel skepticism about world affairs.

The new internationalism which followed World War II produced wondrous results -- the rebirth of Western Europe and Japan -- but it also developed the hubris of empire, the delusion that the United States must take responsibility for everything, every burden, every battlefield. In the Middle West, the idea of imperial America always seemed kind of dumb. With all the natural blessings this nation enjoys, who needs an empire?

But perhaps the debate is opening up a little and the critics will not be put down by the "yahoo" label. I am faintly hopeful because I am beginning to see the questions of alliance raised by "responsible" analysts who describe, more precisely than I can, why the security arrangements between Europe, Japan and the U.S. are confronted with profound contradictions and must change. In the spring issue of Foreign Affairs, a Johns Hopkins professor named David P. Calleo sketches the economic implications of the U.S. military subsidy for Europe. By rough estimate, the United States spends $81 billion a year on the defense of Western Europe. ". . . by any objective measurement of relative resources the United States plays a disproportionate role in European defense," he concludes.

The Europeans like it like that, Who wouldn't? They get to complain about American inconstancy while the Yanks pay the big bills. They postpone the day of reckoning when they must work out their own responsible management of Western Europe security. Calleo writes:

"Obviously, the French, as well as the Germans and British, are loath to trade present arrangements giving them American-subsidized security for a more responsible expensive and constraining role in managing European defense."

Calleo calculates that America could swiftly recoup $30 billion a year in defense spending -- nearly enough to allow Reagan to balance the federal budget, as he keeps promising -- simply by bringing home six of the 10 U.S. divisions.

Bring the boys home? Such talk terrifies the alliance, of course, for it would force our allies and ourselves to confront the most basic questions about western security. What is the real potential for war in Europe? How much is really needed to defend against the threat? If West Germany and France and Britain, not to mention the smaller NATO nations, truly feel the need for those six divisions, then they could readily replace them with their own men. It would cost money, that's all.

My own hunch is an American initiative would force everyone to rethink the basic strategies and discover that much of the war-gaming in Europe is wildly outdated. Unless America takes the first step, we will continue the con game. U.S. leaders will periodically plead for bigger defense budgets and our allies will deftly duck the requests. Why should they behave differently when they know Uncle Sucker is there?

Another penetrating analysis, by Theodore Draper in last winter's issue of The Washington Quarterly, entitled "The Western Misalliance," brilliantly picks apart the pretenses and fallacies which sustain the alliance. The new isolationism, Draper suggests, is in Europe where political leaders insist on American dollars to defend their own countries but prissily draw back from any allied actions to assist the United States in other areas.

While Americans pony up billions to rearm for the Cold War, Western Europe continues detente with the Soviet Union, buying and selling and borrowing. Somebody is wrong here, either us or them. West Germany has become the Soviet Union's biggest trading partner. The Commie nations now owe western banks more than $65 billion. Europe's idea of alliance, as Draper observes, amounts to economic collaboration with the Soviets and economic competition with the United States. Does that make any sense?

Now two new seminal events are upon us, deepening the contradictions. The revolution in Poland, stimulated in part by the western trade fostered by detente, provides an historic opportunity for change. Meanwhile, back on our side, the new French government has four Communist ministers in the Cabinet. In other words, it gets harder and harder for serious people to believe that the Cold War is as simple and straightforward as the U.S. hawks believe. Nevertheless, we are launching our massive military buildup and few politicians have the courage to speak against it. Or even ask basic questions about equity. Uncle Sucker lives.

Peter Jay, the former British ambassador to Washington, put it sharply, describing the European attitude toward America: ". . . it boosted and boosts European morale to spotlight American errors, to savor its failures, to exploit its market, to resent its overseas investments, to have a critic's ringside seat at its global tribulations, to mock its culture, to deride its leaders and to bewail the 'weakness' of its currency."

While we cut food stamps and Social Security. That's what brings out the yahoo in me.