Yet we all seem to understand the actual history of America.
When that happens it usually means that the lack is perceived only, and not reality.
Even when we were in school we learned that slavery was evil and that it happened. We learned about Jim Crow laws and how they too were wrong, we learned about the expansion of America to the West Coast and how the Native population (my father's and by literal DNA extension my own family) was treated. We learned enough about it that Karens in school board meetings and "the triggered" are all around us ready to tell us how we don't know about it, though they learned about it in the same place we did, being taught by the same people, going to the same colleges, high schools, etc.
The history of the United States is a mixed bag, beginning with a very high ideal and falling short from the very beginning, but creating a system meant to improve itself, and it has. While we work towards that future, and someday will reach a damn good proximity to perfection, probably just years before it all falls apart (but I digress).
Anyway, that you know enough to say that we lack some knowledge comes to you because we didn't lack other knowledge and history and while no system has ever reached perfection it is my humble opinion that the United States' system provides the best shot to get there. Even if we let assholes have free speech along with the woke warriors (some would say I just repeated myself there).