China flexed it financial muscle recently, and the markets responded instantly.
The US isn't really a superpower. It just thinks it is one, and has (almost) everyone else fooled.
But it can't afford its current levels of adventuring, politically, financially or socially. There will be a payback period. It may land on the wrong people for the wrong reasons. But even so - I'll be hugely surprised if there isn't an accounting within the next decade, and possibly even within the next couple of years.
Key to the "accounting" is the relationship between the Dollar and Oil.
It HAS to change and soon: I'm two years bid and five years offered
In the meantime, if I were a hedge fund manager I'd be borrowing as many dollars as I could and using them to buy energy assets in any country mad enough (or coerced enough) to sell them...
SO I still give the American Empire a range of 10-40 years.. and if it were to pursue the first among equals policy instead of Empire (with intelligence) .. it could keep on for over half a century (and it could be longer but I do not dare to predict anything 50 years from now)
Other than that, it will be another England/France/Spain at the most within 40 years.
An opinion of the future.. a mere opinion.
A pleasure I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude
...c'est le moment de désespoir où l'on découvre que cet empire qui nous avait paru la somme de toutes les merveilles n'est en réalité qu'une débâcle sans fin ni forme, que sa corruption est trop évidemment gangréneuse pour que notre sceptre puisse y apporter remède, que la victoire sur les souverains adverses nous a rendus les héritiers de leur lent écroulement. » Italo Calvino in « Les Villes Invisibles » "Ne te courbe que pour aimer..." René Char