And nearly 43% of Germans voted for the Nazi party, supported burning books, and murdering 6 million Jews and non-Aryans. Of those around 15% believed the rhetoric, and another 15% were mostly supportive.

They followed a madman (a malignant narcissist) who touted pseudo-scientific racism, totalitarianism, and that world domination was the solution to their economic problems. How did that turn out for them?

There will always be people who want to see the world burn. I would guess it's that same hardcore 15%. It may likely be political terrorism rather than an overt civil war. If Donald Trump had succeeded in hanging Mike Pence publicly, that could have been the start of his civil war. When I think of American terrorism, people like Timothy McVeigh come to mind. A small minority may think they are patriotic heroes, but the vast majority will think they are sadistic terrorists.