Once before, in the spring of 1961, a summit meeting of the two most powerful countries of the world took place in Vienna. John F. Kennedy, still humiliated by the disaster of the Bay of Pigs, and Nikita Khrushchev, brandishing his threat over Berlin, entered into a dialogue, and the Europeans, listening uneasily to the exchange, pondered the consequences of the tumultuous meeting. Had the young American president been intimidated by the aggressive ton taken by the Soviets' No. 1 man? What would happen to the former capital of the Reich?

The meeting in Vienna between Leonid Brezhnev and Jimmy Carter left Europeans indifferent. They expected nothing of it, and all went as expected. The text of SALT II had been drawn up; the signing was nothing more than a ceremony of protocol. For the rest, nobody, learned anything from the alternation monologues as they were reported by the press.

With one incapacitated by illness and the other by Congress and the uncertainty of elections, they could hardly plan for a future that lies beyound their grasp. The first Vienna summit marked the beginning of a durable relationship; the second brings to a monochromatic end an ambiguous period in Soviet American relations: neither real detente nor a return to the Cold War.

The ambiguity is more attributable to the United States that to the Soviet Union: In the absence of a president who is sure of himself and of popular support, the American political system functions poorly. The Soviet system can tolerate the semi-absence of a No. 1 man.

The text of SALT II, once completed and initialed, no longer constitutes either a subject of discussion between Moscow and Washington or a bond between them. The treaty becomes the occasion and the theme of an intra-American debate between the White House and Capitol Hill. The Soviets sincerely hope for the ratification of the treaty. Leonid Brezhnev asserted that no amendment by the Senate would be taken into consideration. To help Carter he will avoid, as far as possible, any initiative in the global hot spots. But he will go no further: When Carter asked Soviet intervention in Vietnam on behalf of the refugees, he received a negative answer, immediate and stark.

Officially, all the European governments approve of SALT II. But that requires a closer look. The French specialists in the Quai d'Orsay are, at the very least, reserved about SALT II, and resolutely hostile to SALT III. The german chancellor hopes for a favorable vote in the American Senate, not because the accord seems to him satisfactory in itself but because he fears the Soviet-American tension that will result from the possible failure of ratification.The other European governments have faith in the American leadership. Would that leadership be shaken, within the American nation, by a rebuff inflicted on the president? I am not certain; if that rebuff expressed a conscious decision by the country, a hardening of the national will, the effects of this crisis between the president and the Congress would not be entirely negative.

Regarding bilateral Russian-American relations, the dialogue alway hits the same obstacle. On the most-favored-nation clause or loans, the president can hardly commit himself before the Senate takes up the treaty. As for the Soviets, they hardly understand better today than they did in 1977 what sort of man Carter is, and what sort of policy he wants to carry out.

Until now, when the heads of the two great powers met, they reviewed the whole world and compared their views. That's what they did this time, apparently. But to what end? In the Middle East Carter, after having sketched out an approach with the Soviet Union, committed himself without reserve in favor of the Israeli-Egyptian treaty. Obviously the Soviet Union supports the Arab states, all aligned against Sadat. The collapse of the imperial regime in Iran certainly constitutes a disaster for the United States and the West, but not necessarily a victory for the Soviets. The Iranian revolution is only beginning.For the time being, the Soviet Union has the better of the United States; neither of the two, or even both of them together, could dominate the course of events.

The interventions - Cuban, Soviet, East German, in Angola, in Mozambique, in Ethiopia - would have been considered by Washington, in the past, to be "aggressions" or "acts of imperialism," offensives that called for an American response. Since the defeat in Vietnam, containment has ceased to be the order of the day or a categorical imperative. Andrew Young declared that the Cuban soliders contributed, or could contribute, to stability. As for Rhodesia and South Africa, American policy suffers from a contradiction that results from circumstances rather than any defect of its own. It seeks to avoid alienating the African states by supporting white rule in Rhodesia or in South Africa, but at the same time it fears the rise of a pro-Soviet regime after the fall of the white government. On the mixed administration in Rhodesia the president and Congress are in disagreement. The Soviets play their own game and will not help the Westerners surmount their contradictions.

The United States and the Soviet Union remain the two sole world powers, the only ones capable of projecting their military force upon any part of the globe. The Soviet Union, in this respect, has overtaken the United States. However, beyond the strategic arms limitations, there are few problems that they can settle alone or that they can usefully discuss. What is the American policy in Vietnam? In Afghanistan? Soviet policy at least offers the advantages of being clear. It helps its friends, it fights its enemies or the enemies of its friends (for example the Khmer Rouges). The United States, following it style of government and its principles, is not in a position to act with the same simple brutality. It condemns the invasion of Cambodia by the Vietnamese, but also the Chinese "punishment" inflicted on Vietnam. To the Inherent complexity of events is added the uncertainty of the president himself and the discord among his advisers.

Why be surprised at the Europeans' indifference? The summit of the two great powers slips toward the banality of the innumerable summits in which the heads of state make sure that they have nothing to say to each other, or nothing other than things that they have already said repeatedly. Today the Europeans are more interested in petroleum imports into the United States than in pseudo-secrets from Vienna. CAPTION: Illustration, The Salt Summit, By Auth for The Philadelphia Inquirer