I think the market demand for war movies is less from consumers and more from the government. The legitimacy of the state relies on every war since WW1 to be framed as good vs evil. That is necessary to keep the country united under neoliberal rule.
Civil war movie is less necessary now that racism propaganda is out of fashion. Also now that the country is more divided than ever and secession is popular again, a civil war movie would just push that division further.
