Europe is much more relaxed about nudity (exposed breasts in prime time TV are fine) but much more restrictive about violence and gore. Instead US companies enforce US standards on us.

Even child porn isn't an easy subject. Everyone can agree that liking 12 year olds sexually is pedophilia and images about that are child porn. But when we are taking about 16 year olds it's muddier since we are taking about child porn outside of pedophilia.

And that's just (north western) Europe who are culturally very similar to the US.

Don't be so sure about that, the first amendment is to categorically prevent any discussion of which speech is appropriate. Saying hate speech is restricted or that pornographic images of children are restricted is starting the discussion that was not supposed to start because it always ends in tyranny.

In the latter case, is child pornography probably indicative of a crime? Absolutely. But banning the images and their dissemination is clearly an infringement of free speech. In the former, banning hate speech is also clearly an infringement of free speech. If someone's actions result in violence or death then punish them after, and divorced from the issue of speech; do not place prior restraint on speech.