The thesis that America’s role in managing the world must decline in the long run as its GDP becomes a smaller percentage of world GDP makes perfect sense. The question is, what then? Who keeps order if we aren’t the world’s policeman?
Realistically, there are two options:
1. Spheres of influence: One could imagine a scenario in which we get the Western Hemisphere, the EU runs itself, Russia controls the former USSR, and China turns its near abroad into vassal states. The concept could work, but it leads to lots of questions. Who would want responsibility for Africa and the Middle East? Would South Korea and Japan accept Chinese hegemony? How do Australia and India fit into this scheme? Who regulates friction among the various spheres? These are all matters that would have to be worked out in practice by agreements among the major powers, and it wouldn’t be easy.
2. Bolster international institutions and the rule of law: If individual nations can’t be trusted to keep order, then international institutions are the only alternative to anarchy and oppression. This approach would undoubtedly require the US to accept more Chinese leadership and input into the rules. The Chinese, for their part, would have to accept more responsibility for issues that don’t impact them directly, agree to interfere in the internal affairs of other states when things get out of hand, and embrace the rule of law more openly.
Without saying as much, Obama’s approach of “leading from behind” through the creation of trade agreements and international coalitions was consistent with the second option. In the long run, it is the best (and certainly least cynical) option to replace the Pax Americana.