Earlier quoted context omitted.
That's a good list of the remmants of dismembered entities, with the exception of the USA, which is relatively young.
The USA is also a remnant of a dismembered entity (or rather composed of one). I can't think of any country that has remained exactly the same throughout history. Nearly every country out there is either an agglomeration of formerly independent entities or used to be part of a bigger entity at some point. Your categories are useless. Unless you're trying to define categories for countries which don't exist.
What categories are those?
The USA is no remant, they earned their independence. I don't quite get the "composed of one" part.