FOR the past decade, many observers have predicted that the bipolar rivalry between the United States and the Soviet Union would gradually be supplanted by a multipolar political universe. The rise of a united Europe and a reunited Germany and the concurrent emergence of Japan as an economic giant suggested that there would soon be several superpowers, and none would predominate.But with Soviet communism's collapse and the reassertion of US military dominance in Iraq, these predictions have been thrown into question. We have moved from a bipolar to a unipolar universe, with the US alone now occupying the central position. Even few America-centric ideologues imagined that the American century would be reborn so soon after its declared demise. The reasons are several. Prospective challengers are now disabled or preoccupied with internal transformations. Germany finds its hands unexpectedly full with bringing its eastern third up to speed. Scandal-ridden Japan wavers in indecision - an economic superpower without a mission of its own in world politics. The Soviet Union's virtual surrender on all fronts leaves the US without any substantial opposition on the world stage. How long this political configuration will persist is hard to predict. Perhaps 10 years, maybe less. Germany's reintegration will be complete by then and its perceived weight in the world more substantial. Though still far from complete, the integration of Europe will likely have already created the largest and most influential marketplace on earth. Whether it has resolved its identity crisis or not, Japan assuredly will have further increased its global economic leverage. With the worldwide triumph of corporate capitalism, three giant mergers in fierce competition with one another may effectively rule not just individual nations but whole clusters of allied economies - America, Inc., Europe, Inc., and Japan, Inc. Hence, the world may be neither bipolar nor unipolar but tripolar, with developing nations still left largely out of the game. But that is all in the future. The more immediate question for Americans is what to do with our windfall. We must first understand that this revival is a fleeting phenomenon. Unless wisely invested, the inheritance from our cold-war victory will soon be exhausted and we will find ourselves in hock as never before. We would do well to approach the exercise of our immense political influence and economic clout with the frugal wisdom of the conservation ethic. We should see ourselves as stewards rather than masters of the planet, whose task is to help sustain ourselves and our fellow beings "unto the seventh generation." We must also realize that the renewed adoration of all things American does not represent history's verdict that we have found any final answers to the perennial question, "How shall we live?" The only way to become truly worthy of emulation is to unflinchingly face our own domestic difficulties and determinedly set about resolving them. But as the world's uncontested leader, the US also cannot escape its responsibilities to the global community. As never before in human history, we are faced with supranational crises in which only united, comprehensive action will succeed. These threats range from global warming and arms proliferation to overpopulation, poverty, disease, and hunger. Up to now, the Bush administration's response to such crises has not been that of a leader but a laggard. The US is often the sole nation blocking action on the most vital global issues of our time. In the case of global warming, just one White House advisor, chief of staff John Sununu, appears to be blocking a global consensus on a series of decisive remedial steps on which all other nations have agreed. In the case of arms proliferation, the Bush administration has vastly accelerated sales of US weapons abroad. The lion's share of these weapons flows into the hands of those very Middle Eastern nations that are most likely to use them against one another in an all-too-probable war. In the case of aid to developing nations to combat overpopulation, declining resources, underemployment, hunger, and poverty, the US contribution ranks 18th among the 24 leading industrialized nations in relation to the size of its economy. At 0.18 percent of GNP, the US is far below the target of 0.7 percent long ago agreed upon by all UN member states. Moreover, the vast majority of US economic assistance is concentrated on just four strategic allies, three of them patently undemocratic - Israel, Egypt , Pakistan, and El Salvador. These policies - which US administrations have pursued for many years - are not aberrations from an otherwise far-sighted strategy but expressions of a short-sighted world view framed within a narrowly defined national interest. This interest all too often serves only a privileged sector of the American people and an even smaller segment of the world's peoples. Ultimately, such policies disserve everyone, even those few who in the near term appear to benefit from them. Occupying the center of a temporarily unipolar universe confers special responsibilities on a nation. The ever-intensifying interdependence of all realms of human life obliges us to "think globally and act nationally." In the long term, the national interest cannot be achieved without also meeting the global interest. Whatever course we choose, there is no way to hold on forever to this moment of national supremacy. What will endure is not the fact that American power achieved a fleeting revival at the end of the 20th century but the consequences of how this nation used that power. Recognizing both our responsibilities and opportunities, will we use our inheritance to foster a more balanced and enduring prosperity for both ourselves and the world beyond our borders?