Understood this way, the US is not merely a, or even the, dominant and most powerful actor. Rather, the US offers a genuinely alternative system of international peace and security. And the dominant actor’s willingness to extend a security guarantee to a sizable portion of the planet, explicitly and implicitly, alters the meaning, necessity, and quality of collective security at the UN itself. They are two different game-theory scenarios – a dominant actor within a UN collective security-defection international relations “game”; versus an actor that offers its own security package alongside that of the UN in a parallel collective security “game.” In a diplomatic system characterized (in game theory terms) by insincere public promises, easy defection, moral hazard, and free-riding, the fig leaf is assiduously maintained that the UN constitutes, or anyway offers, a collective security system. Whereas in fact, most leading players in Europe, Asia, and Latin America, and even the Middle East, are unwilling to test the strength of that system: insincere lip service to the UN system while actually relying on the United States.
A realist might say, in other words, that for all the extant elite complaining and populist anti-Americanism, a remarkable number of countries have counted the costs of adherence to the US security promise and found it rather better than their own, and better than the UN’s, and better than anything else on offer, as to both benefits and costs. After all, the US does not even particularly care when those under its security hegemony (which extends far beyond its allies or clients to provide, perversely, significant stability benefits even to America’s acknowledged enemies) heap abuse on it (justified or not) because, in the grand scheme of things, it understands (however inchoately and inconstantly) that the system incorporates (often heartfelt but, in the final policy result, insincere) public rejection and protest by the system’s beneficiaries. The US is not imperial in a way that would cause it much to care. Part of accepting US security hegemony by its beneficiaries includes their rational desire to displace security costs onto another party, even if that providing party thereby has equally rational reasons to look to its own interests first, since it so overwhelmingly pays the costs.
Acceptance also includes realistic appraisal of the alternatives: would Europe (let alone Japan, South Korea, Taiwan, Indonesia, India, the Philippines, New Zealand, or Australia, or even Russia) prefer, for example, Chinese hegemony to the US? The crisis in Georgia forced a little bit of discussion – less than the current newspaper headlines suggest, however – on the mission and role of NATO. On the one hand, Europe is in strategic disarray with the reassertion of regional Russian imperial will; the interests of those close to it are different from those far away and at some point even the United States will wonder, as a matter of budget and defense plans, what NATO is worth: how long does a hegemon support its free riders?
One argument for the multilateralist position is that it will force the rest of the world countries to take a long, very close, look at their present defense structures. Then they will have to decide if their present independence is worth the costs of accepting America's very loose hegemony, or a much tighter one of either Russia or China.