LONDON -- Americans...Don't you just love to hate them? They preach to you about the virtues of an open trading system and then they slap a bizarre set of sanctions on trade rivals before the World Trade Organization makes its report. They lecture the world about the virtues of the rule of law and when their air force is responsible for the death of 20 tourists in Italy, U.S. military courts set the culprits free. But as infuriating as such behavior undoubtedly is, the rest of the world has no choice but to get along with the world's single superpower. The ability to get the United States to behave better in fact is in the hands of America's most frustrated allies.

The root of the problem with the U.S. is that the world has never seen such a unipolar moment. It is only in the past 150 years that great-power politics have been played out on a global stage. Only in the last 100 years has the status of a great power begun to be seen as requiring some form of global reach. In earlier eras, there were a series of roughly equal powers constantly vying for supremacy and alliance. For a time, a Japan or a Germany might have dominated a region, but not for long and never outside its home base.

During the Cold War, we got down to two powers, and by 1991 there was only one. Thus, for the first time since we have had an important degree of globalization, there is only one global power. You don't have to be a great theorist or philosopher to see that we are now struggling with a major structural change in global order. But in each major category of power, there are benefits as well as problems in having one dominant power.