Since there's not much here, I'd recommend asking /r/arthistory
If you compare 17th-18th century art in America and Europe, you can see a trend of battle scenes versus lounging nudes. I'm sure art historians would have resources explaining why cultures were diverging this way.
Follow up question, does America's social conservatism stem from being decedents of puritans?
What the hell happened here?
In the US the tv ratings are modeled after the MPAA http://en.wikipedia.org/wiki/TV_Parental_Guidelines
These are some complaints that speak to the issue of the MPAA being more concerned with sexual content than they are with Violence
for those interested "This Film is not yet Rated" is a documentary that explores the issue http://en.wikipedia.org/wiki/This_Film_Is_Not_Yet_Rated
Also it's worth mentioning that the MPAA is a private group created by the film industry, I think some europeans countries are state agencies but don't quote me on that.
"European countries grew to censor violence" any source for this or reason for this assumption? I don't see it being true at all. There are lots of gun fights in Cobra 11 (German series) for example. And NCIS, CSI and similar stuff is broadcasted without much censorship to the extent that I have to look out what we watch during dinner as a full on autopsy is a poor accompaniment to my meal.