Over and over again we have criticized the fallacy of comparing the roman empire with the supposed american ’empire’.
The false analogy arises from many sources, but the most direct is the incorrect periodization that compares the roman republic to the american, then jumps to the period of the roman empire. These are all very different things.
The american ’empire’ is a form of capitalistic imperialism in the sense of the legacy of early modern versions which did not generally indulge in the total conquest and assimilation of the roman phase.
Technically it is useful to distinguish imperialism and empire.
But any comparison must look at the time scales: the roman republic endured for six centuries before turning into an empire, and by that reckoning the american republic is still a republic and would continue for many centuries more before turning into an empire, assuming the analogy had any basis. The current state of the american system is not decline in the sense of the roman empire, but a kind of corruption of capitalist oligarchy.
In general the comparison of rome and american is a waste of time, and confuses all who write on the subject