As Orrin Judd notes, American declinism is coming back in to fashion (although it’s never all that far out of fashion). To some extent this is the legacy of former President Jimmy Carter, who did more than anyone else to legitimize this line of thought.
In my view, what most of the declinists miss is that the American Hegemony is unlike any previous empire in its structure and means. The former British Empire is the closest, but it still depended on far more direct control than the American Hegemony. The USA has little need of directly dominating its client states, as empires have done in the past. The essential point is that liberal democracies empower the USA regardless of the actual attitude of the government. Even Old Europe is of net benefit to the USA, despite the overt hostility of its two largest states, France and Germany. This creates a dynamic of low effort, high reward that eliminates the problem of imperial overstretch.
Let us consider Western Europe for a moment. The presence of imperial troops there is not for our benefit but for Western Europe’s. In contrast to previous empires, the USA would in fact be better off if its troops were removed from the area, except for a token amount. When the imperial dynamic is less troops, better payoff, it’s hard to see where the overstretch comes in to play.
Of course, there are places and times that demand a large military committment from the USA. But these, again unlike previous empires, are limited in place and time. While we had to maintain troops for decades in South Korea to protect our interests, we could now (as in Europe) pull out all but a few without little or no cost to our security interests. I don’t see Iraq being any different. It may well be decades before we can drop our military efforts there to token levels, but on the time scale of empire a few decades is a but a moderate length of time. It will certainly not be the kind of endless, low level grind that, in large enough number, have brought down previous empires.
Why do the declinists miss this? We could point out their fundamental hostility to the USA, but that’s not an interesting avenue to explore. While certainly part of the reason, it’s not the entire reason.
We can begin to see the root of it if we notice that the American Hegemony is local Anglosphere politics writ large. The Hegemony is much more like a village of free but cooperating people in the Anglospheric tradition than the various forms of despotism that formed the structure of previous empires. I think most of the declinists can’t see this because they come from a Leftist tradition that cannot envision a society of freely cooperating individuals and so have no model for the same thing among nations. As Adam Smith pointed out, a collection of free invididuals naturally benefit each other, via trade and other interactions. In the same way, a community of free nations (externally and internally) benefit each other without any need for explicit control. That is the missing concept that informs the declinists’ world view.
One can see this most clearly in the structure of the European Union. This project is to a large extent an effort to duplicate the success of the American federal structure. Yet it is a failure precisely because it consists of ever more centralized control. When it was the European Economic Community, i.e. like the Anglosphere, it was of great benefit to Europe. But now that it is becoming true to its roots as a poor imitiation of the American Hegomony with the centralized structure of previous empires, it is the EU that is beginning to falter from imperial overstretch, exhausting itself fighting endless battles against recalcitrant populations.
The American Hegemony may not last forever, but it’s certainly going to outlast any of its existing competitors.