Firstly, female genitalia is very rarely shown in films, I think it's probably actually more rare than male genitalia. Yeah, you might see female bodies nude from the front more often than males, but usually you can't actually see the genitals when a woman does that.
Secondly, in the OP you specified in sex scenes. It seems that they usually avoid showing genitals in sex scenes. If genitals are shown it will almost always be in a non-sex scene. I think there's considered to be a fine line between a sex scene and porn, and to avoid crossing that line they avoid genitals in sex scenes.
Also, I agree the whole "US is so conservative" trope is outdated now. It was true in the 90's and 00's, and maybe before. Nowadays US entertainment is packed with tons of sex and nudity, probably more than anywhere else (and also it's so often gratuitous and done for titilation, which wasn't the case in European shows and movies most of the time, in European shows it would normally be a case of "Well, the character would be naked at this point, so the actor will have to get naked", in the US it's more like "Let's get this hot actor/actress to get naked a few times". You can also see the difference because US nude scenes are almost always extremely flattering to the actors, making them look as sexy as possible, with lighting, angles, making sure the actor has pumped muscles, etc. whilst European nude scenes try to be more realistic and often arent flattering to the actors).
It's pretty much at the point now where every attractive American man gets naked, even non-famous ones. Whether it's for a photo-shoot, leaked nudes, nude scenes in TV/film, OnlyFans, just self-posted ass pics on Instagram, etc. It's at the stage where I am actually shocked when I find an attractive American guy who hasn't done nudity. In other countries it's not THAT common.