It depends on which story you buy. An American in 1925 considered America a "shining city on a hill" relative to corrupt old Europe. That American was doubtless

It depends on which story you buy. An American in 1925 considered America a "shining city on a hill" relative to corrupt old Europe. That American was doubtless isolationist. After the heavy propaganda campaigns to get Americans to accept WWII, that's no longer been the case but there is cognitive dissonance. The leadership does not always have conveniently available justification. There were Congressional hearing on Vietnam through the years, and various CSPAN channels run them. It's worth learning the language from there.