It is about reward structure. Ghengis Khan had gold and fortune to pillage from all the nations he conquered. He forced his ideals upon others but his will was

It is about reward structure. Ghengis Khan had gold and fortune to pillage from all the nations he conquered. He forced his ideals upon others but his will was absolute and his moral compass never involved giving a shit about those you crush in battle. The US is still somewhat run by people - a lot of work has gone into dismantling legitimate democracy in America, but fundamentally I doubt even in the gerrymandered guaranteed seat no choice electorate system the US has today, that the people would idly allow the American military to pillage nations around the globe for gold and jewels. At least, they could not do it as fast as Ghengis did. I do understand a lot of looting happened in Iraq / Afghanistan and in a large part the motivations to go to war there were over possessions of a different kind.