It's true - Europe is much more advanced in terms of accepting nudity and doesn't over-sexualize when it's not sexual. I guess we should maybe count our blessings that we're not as repressed as say the Middle East, however I don't feel like we're making any progress.I personally think we have a large segment of Americans that wish for the "days of old" and as such they've attempted to keep laws that hearken back to the 50's and 60's, when some progress in relaxing morality laws was first being attempted...The UK can be as bad as the US in attitudes to nudity and the assumption it has to be sexual. Nowhere near as open as much of the rest of Europe. But there again we wont be part of a Europe for much longer.
Yet the law is much more permissive than in the US.
To answer why the US and Europe have such diverging attitudes and laws in places, it's important to look at who left Europe to come to the US. Puritans, Calvinists and Catholics make up a large percentage of the founding population, and their ideas are reflected in laws and political positions to this day. That's not the only reason, but it's one.
I agree there is a double standard for male and female breasts and nipples, but that's for some of the same reasons that we see such conservative and uptight attitudes around nude bodies in the first place.
Canada's Supreme Court struck down the breast ban for women many years ago and although it is rare, women are allowed to go topless in public nationwide as men are. The SCOTUS is deliberately applying obscenity to the breast and it's sad.