As an aside, I don't know if there's any US law against showing adult nudity on a website. Maybe there's a rule about users being over 18.
Indeed there's no laws in the US that protect violent images whole covering the body, but that is the cultural standard which has been exported around the world.
I get that you're making a point that, why give control abroad to governments when I'm the US companies self censor?
First, what goes into the hands of companies versus the state also various culturally, and the US does have content laws other than the one you highlighted.
I'm not sure about the violent images. There are definitely rules against showing bodily harm on FB, but I have no idea where the line is.
Notice that your comment equates nudity with pornography. Where I'm from it's not normal to do that.
If there's a social media site in some other country that doesn't have those rules, that'd be a good example.
And they know that language because otherwise they wouldn't be in government.
So the US wants Tiktok to change and uses the language that will resonate with Americans to ban it when Tiktok doesn't fold.
China does the same with the companies it wants to change. That they listen is purely a financial decision.