When the United States is identified as an empire, albeit of a different sort than some others, it's common to point to the fate of ancient Rome or the empires of Britain, Spain, Holland, etc., as a warning to the Pentagon or even to CNN debate moderators.
But a closer analogy to the current United States than ancient Rome, in a certain regard, might be the Vikings. The United States doesn't create colonies in the places it wages war or wields influence. It raids. It pillages. It plunders resources. It manufactures smart phones. It fracks. It sets up isolated settlements, heavily fortified, also known as military bases, embassies, green zones, safe zones, and moderate rebel training camps. It sails for home.
What ever happened to the Vikings anyway?
I'd like to see a survey done on that question. I'm afraid many people would answer that the Vikings died out or got themselves slaughtered or slaughtered each other. That would certainly be an anti-imperial moral for the Viking story. It would also fit with the idea that violence controls people rather than the other way around.