Going into Alex Garland’s astonishing new film, “Civil War,” I expected to be irritated by the implausibility of its premise. I’m not talking about the idea that America could devolve into vicious internecine armed conflict. That seems possible, if not probable. In one 2022 poll, 43 percent of Americans said they thought a civil war within the next decade was at least somewhat likely. I wouldn’t go that far, but I won’t be surprised if political violence spikes after the upcoming election and eventually spirals out of control. I’m pretty confident, however, that if the sort of war Garland depicts ever actually broke out in this beleaguered nation, California and Texas wouldn’t be on the same side.

“Civil War” has received plenty of adulatory reviews, but Garland has also been widely criticized for eliding the ideological forces driving America’s fracturing. He’s repeatedly spoken about the dangers of polarization, a bit of a cop-out, given that only one American political party has leaders who lionize violent insurrection. This month A24, the powerhouse indie production company behind “Civil War,” released a map of the film’s fictional divisions on social media, under the hokey caption “Pledge your allegiance.” It showed an America split among the Loyalist States, stretching from the East Coast through the center of the country; the southern Florida Alliance; the secessionist Western Forces of California and Texas; and the New People’s Army of the northwest, which sounds vaguely Maoist.