Perhaps the UN or some other international body is best suited to regulating social media, these are international companies with a footprint in many countries, twitter, Facebook and the Chinese Tic Toc being some recent examples. No first amendment worries for those who just want to operate inside the USA, or China for that matter. A large majority of international support for this should not be hard to get for something like this, these companies operate what are essentially newspapers inside their borders, these countries would include Canada and most of the EU among others. It would make it easier for the social media companies too, a uniform set of laws and regulations that applied internationally, like the uniform US business code between states.