Said social media apps could probably launch tomorrow if they followed local laws. They don't want to, so they aren't allowed to operate. I can't think of a single world government that would allow a company to operate within their borders without being subject to that government's rules.

However if they did comply and try to do it now they'd probably struggle since China made their own [arguably better in many cases] alternatives since the US companies didn't want to play ball.

I work for an international company. Due to the nature of my industry we had a LOT of new laws and regulations to follow in China, probably more than most social media companies. We did the work to comply and we are more than welcome to operate in China. It is our biggest market by far, and growing faster than any other.