> it achieves power, at the expense of the long term survival of the nation. a weak nation cannot survive without a powerful patron. in fact, empires often encourage nationalism for their vassals to keep out the influence of their rivals, as well as to create proxy armies willing to fight in exchange for a cut of the imperial profits. vassals are economic/military dependencies. you are correct that rome's diversity weakened it internally, but it strengthened it externally. at least until rome could not longer afford to buy off its vassals.
United States