I do not think it is proper to compare America, or any other nation other than Rome, with the Roman Empire. The setting, technology, players, cultures, rules, etc. are just so completely different from that era that it is like trying to compare a gecko with a fish. There are a handful of similarities, but otherwise they are radically different. If you are trying to compare the two because of certain historical cycles, that is fine, but I think it is still far-fetched.