I think the issue comes down to collective trauma and lack of free speech by the oppressed.
The massacre of the native peoples, horrors of slavery and resulting civil war, Jim Crow era in the south, the war on drugs, and the war on terror are all genocides in their own right, but the voices of the oppressed have been silenced in history books and mass media under the guise of ‘keeping the peace’ or promoting unity, while the people who facilitate(d) these things continue(d) to play a role in shaping national discourse.
(Say nothing of ‘lesser’ national traumas, such as prohibition, the race riots of the 50’s and 60’s, the intentional lack of healthcare for the gay community during the height of the AIDS epidemic, and the ongoing class war that’s being executed through education access and cuts to social programs.)
The U.S. has never looked inward, or if it has, it has largely chosen to ignore the lessons that could be learned.
I think that even if there were a nationally traumatizing event of the sort that transformed Germany, the U.S. would gleefully skip past it to repeat the same mistakes.
I believe the issue is not lack of opportunity to learn, but a resistance to learning and a refusal to, as it were, e pluribus unum.