

It was revenge for making Americans feel vulnerable. Two oceans and the world’s strongest military made Americans feel safe from the world (and the effects of U.S. policies toward it). Even national humiliations like losing the Vietnam War were things that happened “out there.” Domestic resistance to the invasion of Iraq often took the form of “Why Iraq when we should be going after the people responsible for 9/11 instead?” Resistance to the invasion of Afghanistan was much more muted for this reason. It was only later that everyone was always against both wars.
No one was willing to give Hitler bad news either.