I think, you, seem to be unaware that in most instances, for Americans, one of the primary points of their educational system is the creation of citizens that will not perceive their country as an empire, but a republic. Generally, if you're feeling really cynical, one could say that one of the primary points of mass education is indoctrination, regardless of the country in question.

So, it's actually rather condescending of you to imply this sort of stuff isn't swept under the rug when, in fact, it actively is right now. Just look at the current American conservative obsession with removing critical race theory from the educational system. The aim is to sweep any nuanced discussion of race as it pertains to America under the rug, that's the active goal. And if you are as knowledgeable as you position yourself to be, then you know that race is a critical factor in the history of American imperialism.

So, no many people are not, as you imply, willfully ignorant of the reality of American imperialism, there are many people with powerful political interests in sweeping America's imperialist history under the rug.