The self-image of the post–Cold War United States rested on the misconception that the disappearance of the Soviet Union left it the same kind of power it had wielded during the Cold War, when the possession of a vast nuclear arsenal was the measure of its special status in a bipolar international system. With the bipolar system gone, however, the U.S. nuclear potential became all but meaningless as a determinant of its status in the world. Instead, America's power in the new international system derived from its huge economic potential and unmatched cultural influence in addition to its military establishment, supported by defense spending that was greater than that of all other nations combined. America's new predominance thus was different from the superpower variety, as conveyed in the French-invented term "hyperpower," implying excess without clear purpose.
The legacy of the superpower era made it difficult for the United States to redefine its global role in the post–Cold War era and relate it to diplomacy. Americans also found it difficult to choose the proper ways of using their military power. On the one hand, they deployed it in some countries where their interests were not clearly involved. On the other hand, they placed self-imposed restrictions on its use by becoming beholden to the crippling concept of minimizing losses of their manpower and matériel and by insisting on the termination of their military involvements at a time of their choice.
Such restrictions made the involvements both controversial and less effective than suggested by America's military power. In the Gulf War of 1991 against Iraq—a conventional war against a regional aggressor—the United States showed a new sensitivity for multilateral diplomacy by being able to form a broad coalition in support of its intervention, but then abstained from trying to press for final victory, much as it had learned not to press the Soviet Union to the wall during their superpower competition. Similarly, it missed opportunities to prevent the descent of Yugoslavia into war by timely use of force sufficient to frustrate Serbian aggression. The Clinton administration, less attentive to foreign policy than most of its predecessors, suffered even more from belated and piecemeal deployment of military power, thus reducing America's ability to influence events. Its reluctance to commit itself militarily in the former Yugoslavia made the eventual American intervention in the Balkan wars more costly than it need have been. Secretary of State Madeleine Albright, misled by notions of deterrence dating from the superpower era, underrated Serb leader Slobodan Milosevic's aggressive intent, leading the United States and NATO to a war for which they were unprepared and only won at high political cost.
Looking back at the long rivalry with the Soviet Union, American officials tended to see rising security threats comparable to the old Soviet one. Some regarded Russia as one such potential threat despite the low probability of its recovery as a great power. Others viewed China as a future superpower because of its size and nuclear capability, regardless of its lack of an expansionist political culture and despite an extensive number of complementary interests between Americans and Chinese. Washington also came to regard otherwise minor "rogue states"—Libya, North Korea, Iran, Iraq—as potential threats on the order of the Soviet Union solely because of the conceivable acquisition of weapons of mass destruction by their dictatorial regimes.
In dealing with these real or imaginary threats, the United States showed the same predilection for regarding them as military rather than political problems that it had shown during its competition with the Soviet Union. In particular, the national missile defense (NMD) project, embraced tentatively by the Clinton administration and unconditionally by the George W. Bush administration, harked back to the Cold War days when the other superpower's inclination to attack unless deterred was taken for granted. The concept of NMD, which assumed that such an intent may develop in the future, was conducive to bringing about the very threat the project was intended to avert. Insufficient confidence in the susceptibility of such threats to diplomatic solutions divided the United States from its allies, thus undermining its leadership position among them.
Unilateralist tendencies threatened important accomplishments of American diplomacy after the end of the superpower rivalry. The United States took the lead in such achievements of multilateral diplomacy as the negotiation of the North American Free Trade Agreement, the establishment of the World Trade Organization, the provision of energy assistance to North Korea in return for the abandonment of its nuclear weapons program, and other international agreements recognizing the growing importance of dimensions of security other than military. As evidenced by the repudiation by the United States of the Kyoto Protocol to reverse global warming, of the International Criminal Court designed to deter crimes of genocide, and of the Comprehensive Nuclear Test Ban Treaty, those achievements proved liable to relapse to the obsolete superpower mentality. The United States had to recognize that, because of the increased relevance of economic and environmental as well as political constraints, the nation was in important ways less powerful than it had been as one of the two superpowers. America's transition from a superpower to the leading "normal" power marked the final demise of superpower diplomacy.