I wouldn't write the U.S. off so quickly. They are the words greatest capitalists, its what their nation was built on, and if they can rid themselves of the lefty liberal nonsense which has infested, and is slowly but surely destroying the western world, theres no reason why they cant rise again and show the Chinese how real global capitalist power is done.
Its a big ask, but if the will is there, its doable.
The U.S. has never been an empire btw. It has been a(sometimes dominant) global power, but thats not the same thing. This may be why it has outlasted the USSR and will outlast the EU, as they were / are Empires.
I didn't call it that directly, as you are right in one way; it has not been an empire in the sense you mean, with land acquisition and colonisation, but it is a type of empire of a financial nature, hence my use of the "empire", with its corporate trading tentacles all over the globe. It also does have "territories" beyond its mainland, for a mainly Strategic purpose, just as in the case of the British Empire.
It is also declining, as empires do, due to internal forces, with the customary "implosion" already happening. The divisions within America are so great that it will tear the nation apart. I predicted in the 1970s this would happen with the CCCP, and it did due to the populous being fed up with a system that was not socially working for them. Britain's empire fell apart due to political and social unrest, due to it not being able to split the Government's expenditure between military and social needs in the early 20th century, and finally the overwhelming debt caused by "winning" the Second World War. This, combined with the demand of the populous for a better, socially aware, democracy caused the British "implosion". The USA is going the same way, but without the major world war effect. Indeed, that last war created the American "empire", but those advantages are now being ground down by the Chinese effect.