Another parallel to consider. Rome defeated Carthage, the other "superpower" of the day while maintaining her superiority, but was brought down by the less-civilized rabble - not nations,
per se - in the north and west, essentially through guerilla warfare. In much the same manner, the US has defeated her major enemies and now remains the world's only superpower. And we are now engaged in a war with less-civilized groups - not nations - practicing a form of guerilla warfare (terrorism).
I hope the US profits from Rome's example. It's not the wars against clearly defined opponents, with clearly defined goals that establish clear victory, but the murky, guerilla-style where noone knows when victory is achieved, where warfare is a perpetual, draining thing, that will defeat us.
Rome defeated Carthage centuries before Christ. Their rival in the 400s was to the East -- the growing Parthian empire in Persia and the Armenian Empire.
Yet another parallel: Illegal immigration. Rome tied to stem the tide of immigration into the empire. Barbarian tribes moved into the empire, and became the enemies "inside the walls."