That’s a pretty classic Marxist understanding of how class conflict actually happens. In response to a crisis a state can either adapt or fall into chaos if it can’t. That’s essentially what happened during the new deal era and the civil war respectively. Although arguably the external threats of WWII allowed the US to adapt rather than fall apart.

I think the line between a liberal democracy and fascism is much blurrier than most people think. I suspect the transition from one to the other, going in either direction, is entirely dependent on how much internal forces threaten the ruling capitalist class.

I think you might be underestimating the number of democrats that are also war hawks who want to bomb Iran.

Yes. It was the largest protest movement in US history and it did precisely nothing to stop police brutality.