Chief among the problems facing the United States today is this: too many obligations piled high without the wherewithal to meet them. Among those obligations are the varied and sundry commitments implied by the phrase “American global leadership.” If ever there were an opportune moment for reassessing the assumptions embedded in that phrase, it’s now.

With too few Americans taking notice, history has entered a new era. The “unipolar moment” created by the collapse of the Soviet Union in 1991 has passed. To refer to the United States today as the world’s “sole superpower” makes about as much sense as General Motors bragging that it’s the world’s No. 1 car company: Nostalgia ill-befits an enterprise beset with competitors breathing down its neck. Similarly, to call Barack Obama the “most powerful man in the world” is akin to curtsying before Elizabeth II as “Queen of Great Britain, Ireland and British Dominions beyond the Seas.” Although a nice title, it confers little by way of actual authority.

A new global order is rapidly emerging. In that order, the United States will no doubt remain a very important player. Yet alongside the United States will be several others: China pre-eminently among them, but with Russia, India, Turkey, Japan, South Korea and Brazil also demanding to be reckoned with. (Whether Europe, currently wallowing in disarray, can muster the will and wallet to play in this company qualifies as an unknown.)

Nothing Washington can do will prevent this geopolitical transformation. For Americans, husbanding power rather than squandering it is the order of the day.

That said, there is much that the United States can and ought to do to ensure that this emerging multipolar world ends up being more or less stable, and more or less decent, and therefore more or less congenial to the well-being of the American people.

In that regard, spending hundreds of billions of dollars vainly attempting to pacify Afghanistan is unlikely to help much. Far more useful (if hardly less challenging) might be the following:

Negotiating “boundaries” — constraints, for example, on the use of force — that will limit great power prerogatives (including our own) in the 21st century.

Establishing norms governing the competition for increasingly scarce natural resources.

Reducing armaments and curbing the international arms trade, thereby restricting the availability of the hardware that sustains wars once they begin.