The MPAA is an American based classification board which they determine the age rating of a movie, but does that apply to let’s say K-Drama or Japanese anime containing themes they consider “inappropriate” for American viewers when they don’t take cultural nuance into consideration. As in you can have a “underage” looking character in anime being sexualized but that work gets accused of glorifying pedophilia in the US.
The predecessor of the MPAA is the Hayes Code, which is even worse with censorship as they sanitize the hell out of movie production (love stories barely have raunchy scenes or violent movies showing no blood) but that only applies to productions from Hollywood while foreign movies are not bound by those rules. Can you create a movie similar to the “Serbian Film” while overseas but will it be approved by the MPAA for theater screenings?


So I was going to say that in general theaters won’t play films that are unrated or rated NC-17, although you might get a small independent theater to play an unrated film.
However in article discussing the film Terrifier 3,
So it sounds like an unrated film could play in a major theater. However the film Terrifier 3 is a horror film and likely has a lot of violence, which culturally speaking Americans are more ok with. Your example is around sex which Americans are usually more taboo about.
Obviously it depends on the film, but I think if you made a film you think would get an NC-17 rating, you’d be better off releasing it as unrated and then trying to convince (major) theaters the film will be successful enough to make money in order to get it shown.