Robert Kagan, in Foreign Affairs:

Those who today proclaim that the United States is in decline often imagine a past in which the world danced to an Olympian America's tune. That is an illusion. Nostalgia swells for the wondrous U.S.-dominated era after World War II. But although the United States succeeded in Europe then, it suffered disastrous setbacks elsewhere. The "loss" of China to communism, the North Korean invasion of South Korea, the Soviet Union's testing of a hydrogen bomb, the stirrings of postcolonial nationalism in Indochina -- each was a strategic calamity of immense scope, and was understood to be such at the time. Each critically shaped the remainder of the twentieth century, and not for the better. And each proved utterly beyond the United States' power to control or even to manage successfully. Not a single event in the last decade can match any one of those events in terms of its enormity as a setback to the United States' position in the world.

The September 12 Paradigm