ONE OF THE surprises which greet a foreign visitor to this country is how little confidence Americans have in their ability to deal with the Russians. They always seem to think they are being outsmarted in negotiations, overtaken in the arms race or outmaneuvered in the Third World. Even when they win a victory they seem determined not to recognize it.

A pertinent example is the attitude of many American scholars, politicians and editorial writers to the 1975 Helsinki agreement, which is now emerging with signs of new life from a three-year review conference in Madrid.

This elaborate document on security and cooperation in Europe -- weightily named the "Final Act" -- was hammered out between 1972 and 1975 by 35 nations of East and West, including the United States and the Soviet Union, and was then signed by heads of state in Helsinki.

It originated from the desire of the Soviets to legitimize the postwar frontiers of Europe and their own control over Eastern Europe. However, stubborn and skillful Western negotiators gradually turned Soviet drafts into something completely different: a charter for change which obliged the signatories to respect human rights, sovereignty and self- determination and to promote a wide range of contacts between their peoples.

Yet almost every time the document is mentioned in this country it is treated as if it conceded Moscow's main demand in return for empty promises to respect human rights.

For example, Prof. Seweryn Bialer of Columbia University writes in a recent book that "Soviet rule over its empire was legitimized internationally at Helsinki in 1975." In the view of Prof. Gail Lapidus of the University of California, "the Helsinki accord of 1975 . . . in effect, recognized Eastern Europe as a Soviet sphere."

Here is Time magazine of last Nov. 22: "At the 1975 Helsinki Conference on Security and Cooperation in Europe, (Soviet leader Leonid I.) Brezhnev obtained long-sought legitimization of Soviet rule over its empire." And here is William F. Buckley Jr. in Foreign Affairs in the Spring, 1980, issue: "The Helsinki Accords . . . gave the Soviet Union what it had wanted for so long, namely de jure recognition of the postwar frontiers."

Wrong, all wrong. When challenged, most people point to the passage in the agreement which says that "all participating states regard as inviolable all one another's frontiers as well as the frontiers of all states in Europe and therefore they will refrain now and in the future from assaulting these frontiers."

But this simply means what it says, namely that frontiers should not be attacked, a principle that is in the United Nations Charter.

So the Final Act, which has no legal force, adds nothing to the legality or permanence of the frontiers, which were recognized (with reservations) by West Germany in treaties signed with the Soviet Union and Poland -- and endorsed by the Western allies -- before the Helsinki conference.

Indeed, the Final Act makes a special point of saying that frontiers "can be changed, in accordance with international law, by peaceful means and by agreement." Thus, if it says anything new about frontiers it is that they are not automatically regarded as permanent. And of course, if the Soviets were to respect inviolability they would have to give up their habit of invading their allies, so their control would be weakened.

But the frontiers have little to do with the central issue of Soviet hegemony over Eastern Europe. This was dealt with elsewhere in the Final Act. Soviet negotiators tried long and hard to legitimize their claims by arguing that the principles of good behaviour set out in the first part of the Final Act should apply only to relations between states with different social systems.

Had the Western negotiators accepted their drafts the Final Act would indeed have legitimized the "Brezhnev Doctrine" formulated to justify the Soviet invasion of Czechoslovakia in 1968. It would have meant that none of the obligations to respect human rights, sovereignty, self- determination and all the other principles would have applied to Soviet relations with Eastern Europe, only to East-West relations.

The Western negotiators saw this clearly, resisted and won. Their victory was embodied in the highly important preamble to the first section (known as Basket I) which states that the principles shall be applied to relations "with all other participating states, irrespective of their political, economic or social systems. . . ." In other words, the Soviet Union has no special rights in Eastern Europe.

There are some passages recognizing the rights of states to determine their own laws and regulations, which might be interpreted as inhibiting the West from challenging the more blatantly repressive laws of Eastern Europe. But the rest of the Final Act is so full of support for human rights and contacts and the right of peoples to self-determination that it is impossible to regard the document as endorsing the status quo. If observed, the Final Act would transform Europe.

How much has actually been achieved in practice by the Final Act is, of course, a debatable issue. But it is puzzling that so many Americans resolutely refuse to recognize a diplomatic victory when they see one. Perhaps one of the reasons for trans-Atlantic misunderstandings is not, as many Americans suppose, that West Europeans are being terrorized into subservience to the Soviet Union but that, being geographically closer to the failures of socialism, they find it easier to believe that they are on the winning side.