One problem is that the Wiemar Republic had a trillion different parties, which further eroded their democratic institutions.

That's an argument for rank-based voting.

But it's also the only thing that prevented the Communists from coming to power, they were in majority. Hitler did everything he could to convert the Communists - that's what all the low-IQ marching and chanting was about.

Communists would have still won the 1933 election if SPD and KPD were to unite. They were all cut-throat Marxists, and their disagreement was minor. Don't believe the Bernietard propaganda about "social democracy" - Lenin, Trotsky, and Stalin called themselves "social democrats" too!

Social Democrats aside, do you think Trump supporters would've been for or against the Republic?

Maybe my right-libertarian background is showing. Do you want everything dictated from Berlin Washington DC, or to have more power in state and local governments?

In both cases (Germany since the unification, and gradually in the US), the Federal government had grabbed far too much power. Both needed a more decentralized Republic with a stricter constitution (like Switzerland).

Trump supporters are only "nationalist" in the sense that we don't want bad ideas from Europe (socialism) and we don't want Communist China to take over the world. The Demonrats are the real "nationalists": they want to do everything on the national level, and would use military force to crush any secession.