Realistically though the US left isn't big enough, organized enough, or armed enough to even overcome Chud militias, never mind whatever elements of the military and police side with Trump.

Drawing from history, the best bet is something like what Mao did. He didn't fight the Japanese head on, but waged an effective guerilla war mostly independently of the Nationalists while building a political and military base. Sub in the libs for the nationalists and trumpists for the Japanese.