THE dramatic changes in the Soviet Union are creating new tensions among the United States and our erstwhile cold-war allies. These tensions reflect fundamentally different perceptions about how to respond as the old Soviet order has been swept away.To a considerable extent, the US seems to prefer to deal with the last vestiges of that old order and seems reluctant to engage the new nationalist and ethnic forces that are emerging throughout the country. American businessmen and politicians are generally unimpressed with the economic potential of the country; perhaps more accurately, they see nearly endless problems before that potential can be realized. US diplomats seem to worry more about the possible consequences of the disintegration of central control of nuclear weapons than about long suppressed desires in many parts of the country to be free of Moscow's rule, whatever form that freedom might take. In part because of America's budgetary problems - but also because of an apparent conviction that any substantial amounts of money would simply be wasted - until recently President Bush has been unwilling to advocate large-scale financial aid for the Soviet Union, arguing that political stability and economic reform must precede substantial aid. The tone of American statements on aid changed in recent weeks, with the US offering debt relief and urging that the International Monetary Fund (IMF) and World Bank lead any international assistance program beyond immediate humanitarian needs. But, as every debtor country well knows, IMF leadership usually means a stronger emphasis on austerity and restructuring than on large-scale aid - and the Soviets are incapable now of serious economic restructuring. For their part, the Japanese are highly skeptical about the Soviets' ability to resolve their crushing economic, political, social, and ethnic problems in an orderly (i.e., Japanese) fashion. Tokyo is worried that the international community will look to Japan to finance a major part of the rehabilitation of the Soviet economy, a prospect made all the more unattractive by lingering animosities from the Russo-Japanese war and the continuing Soviet occupation of the Northern Territories. The Russians may eventually offer a deal on the islands that politically Japan cannot refuse, but there is little enthusiasm in Japan for large-scale aid to the Soviets. Even the recent Japanese commitment of $2.5 billion in emergency aid and trade credits looks more like an effort to stave off greater requests than an embrace of the notion that Western money can solve Soviet economic problems. THE European view, especially Germany's, is fundamentally different from either the American or Japanese perspective. Europeans see substantial commercial opportunity in a market of nearly 300 million people and vast natural resources, as well as great risk that a further Soviet collapse would stimulate a massive westward flow of refugees. There is a palpable sense among politicians as well as businessmen in Europe that Russia and the other main republics will be able to reconstitute and reform themselve s and, sooner or later, become part of the new Europe. In the meantime, the Europeans are willing to provide substantial finance to minimize the damage that might follow from a more rapid economic decline. These differences, deeply rooted in history and geography, will not soon disappear; indeed, they are likely to intensify as the Soviet situation inevitably becomes more confused. The effect will be to accentuate the tendency that already exists for each of the leading industrial countries to move in its own direction, to maximize its own national interests, and to apply its own policy preferences and priorities. In practical terms, this means that Russia and the rest of what Russian leaders now like to call the "former Soviet Union" are likely to become increasingly dependent on Europe in general and Germany in particular for financial support, trade opportunities, and political direction. If this evolves into a permanent rapprochement - which would run counter to at least the last 100 years of history - the consequences would be enormous. In the (very) long run the result would be to enlarge Europe's relative w eight in whatever new world order gradually emerges. In the meantime, though, it would be a formula for more friction and even less coherence among the US, Europe, and Japan. Unfortunately, the result could be an even more dangerous and accident-prone world than the one from which we are emerging.