NICARAGUA AMERICA’S ROLE : We’ve Done All We Can--or Should : The Caribbean and Central America, always the backwater of U.S. policy, won’t suffer if the <i> Yanquis </i> finally go home.

Is it possible that the United States now might begin the complicated but rewarding task of withdrawal from Central America? The Nicaraguan affair has ended in undreamed-of success for Washington’s allies and for President George Bush--who knew enough not to overwhelm Violeta Barrios de Chamorro with American money, advice and handling.

The Sandinistas are out, democracy vindicated, the Soviet Union all but gone from the scene. There will be no more arms transiting Nicaragua to El Salvador. That international communist threat to Brownsville, Tex., about which Ronald Reagan used to speak so feelingly, has been lifted. What more could Washington want?

Problems persist, but on an uncolossal scale. The Nicaraguan economy is a wreck, thanks in considerable measure to U.S. sanctions. Chamorro’s coalition is a fantasy of political coloration, and setting up a working and lasting government will be tricky. The coalition could itself divide, and Nicaragua could yet find itself with a new government including Sandinistas.

It is conceivable that before it is all over the Ortega brothers might again take to the mountains. Dealing with a politicized Nicaraguan army is a serious problem, and disarming the Contras in Honduras a headache--although nothing like the headache it would have been had the Sandinistas won the election.

Obviously, aid is owed Nicaragua, Washington having done so much there, as in Panama, to produce the present economic wreckage. The war in El Salvador goes on, although after what has happened in Nicaragua, the militants of the Farabundo Marti National Liberation Front must see their prospects in a different light. Fidel Castro is still impenitently what he has been for 30 years, but Cuba’s revolution is atrophied and dying, and Soviet interest in Cuba slight and fading.

That the Nicaraguan election has been a famous victory will undoubtedly encourage Washington not to withdraw at all, but to stay on as patron of emergent Central American democracy. But that role has a limited future. The fundamental problems of the region remain largely what they have always been, providing thin soil for democracy’s growth. There is poverty, the inequitable distribution of wealth, an affronted nationalism, monoculture, a lack of suitable exports, competition on world markets and, above all, a disabling lack of pluralist, democratic political tradition.

There is not a lot the United States could do about these things even if it were prepared to spend a great deal of money in Central America--which, as we all know, it is not. What should count is that the ideological and strategic struggle (as the United States has defined it) is over. That struggle was the reason we said we were there; its end is the reason we can leave.

In the 19th and early 20th Centuries, U.S. interventions had commercial motives, plus the strategic interest in a canal across the isthmus. In recent times, Soviet communism was seen as the force behind Latin American leftism, or at least as the force that would profit from it. When Fidel Castro proclaimed that he was a Communist, an ally of Moscow, for Washington, the geopolitical case was proven and a new program of anti-leftist as well as anti-communist intervention was justified.

However, the politics of Central America and the Caribbean have never been a matter on which ordinary Americans feel strongly. President Reagan may have tossed in his sleep in worry over Brownsville, but people in Brownsville do not seem to have been very anxious at the threat posed to them by Nicaragua’s Sandinistas. Fidel Castro at first was quite a popular figure among Americans, when he came down from the Sierra Maestra and dictator Fulgencio Batista fled in fear.

Ordinary Americans were never that comfortable with Batista, or with the other petty despots the United States seemed persistently to find itself supporting in Central America and the Caribbean: Trujillo in the Dominican Republic, the Somoza family in Nicaragua, Panama’s Noriega. They may have been “our� SOB’s, as Franklin Roosevelt said--but why did we have to have “our� SOB’s?

The interventionist Central American and Caribbean policies of Washington have originated from the top, not the bottom, of U.S. political society. The assassination campaign against Fidel Castro in the 1960s, when Lyndon Johnson discovered the United States operating “a damned Murder Inc. in the Caribbean,� was the result of private obsessions in the Eisenhower and Kennedy Administrations. It was not something the public was clamoring for. It was a big secret because Washington knew the public would be horrified by it.

While successive Administrations have been frightened of giving their opponents ground for saying they had “lost� such-and-such country to communism, it is hard to argue that the popular majority in the United States really cares much about what happens in Central America. It is one area in which an Administration has a relatively free hand--much freer than it has with respect to the Soviet Union, Israel, Europe, Japan, even South Africa.

Thus it would be possible today for the Bush Administration to begin, quietly, gradually, undramatically, to walk away from Central America. It could do so in prudent confidence that Central Americans will, in all, be happier without the Yanqui than with his presence. Washington could declare a victory and go home. The Soviets already are going home. The press then would go home. Silence would fall, the cries of private grief and passion of Central Americans and Cubans unheard in--uncomplicated by--a wider world. Thus do cold wars end.