i think it has to do
with the general puritan "morals" that have prevailed in this country since its inception.
war is something that until very very recently was basically glamorized, while sex is seen by christianity to be something base and profane.
western religions used war to promote their religion, which suppressed sex.
this is all just thinking out loud, of course. there are certainly countries like france and italy, which are very catholic, but not as repressed.
of course, america was built on the protestant religions, which are more puritanical (right?).
and then again, nobody thinks the chauvinist jerks in italy who hoot and holler at every woman are anything to strive for.
but getting back to my first point, war is celebrated. hence, violence. this country was literally built on war, from 1776 (and earlier) thru the decimation of the natives and the glorification of the cowboys.
and it's easier for career politicians (now i'm thinking of the early to mid 20th century) to make a case appealing to puritan ethics by admonishing sex, but how can they even pretend to admonish war as they send troops into battle and need to rally the country around their effort in order to keep up the wars?
so sex gets legislated and violence (war) becomes an accepted norm.