The politics are left intentionally ambiguous because of the point of this film is not to address the political divides that would lead to a civil war but what the consequences would be on the population and in particular the journalists covering it. All we really know about the President is that he has deliberately fostered discord, is serving an unconstitutional third term, and is cowardly in the face of imminent death. If that sounds like someone presently in the public eye it is purely a matter of viewer interpretation.
Another thing about this movie is that it imagines a coalition between Texas and California. I think it’s to make the situation ambiguous since the two states rarely agree.
The political leanings of most characters seemed somewhat ambiguous, including the POTUS.
As for the film, I recall it having a hyper-realistic quality to it, which was a bit unsettling at times (and not in a good way). The one scene that really stood out was the “What Kind Of American Are You?” scene with actor Jesse Plemons.