Yeah, and the Roman Empire lasted until 1453, but that doesn't mean what people think of when they say Roman Empire didn't collapse in 476 (and the Byzantine Empire in 1204).
Whatever's left of the USA in a few decades might call itself USA (well, one or two bits of it might, others most definitely won't), but it evidently won't be the USA as we understand it today, and neither would any hypothetical future union or coalition of those fragments.
