I really hope they don't do that. As far as I know all of the past empires and long-lasting civilizations achieved their longevity and greatness by militarily and economically dominating those around them. We have at least one thousand years of existence yet to be lived before we could be compared with those former great civilizations. You think Texas will go another thousand years without seceding?
The effects on those being dominated are generally culturally and resource severe, and long-lasting. The Philippines could be a modern case in point. They were dominated by the Spanish as a colony, and then by the US following the Spanish American War in 1898. You can read a brief history here:
Spanish