A number of countries already ban specific social media sites, including US based social media sites. In many cases, the core issue is that the country wants foreign social media sites to obey local laws and instructions on what to ban. And if the social media site refuses, it is just wholesale banned.

Leaving aside whether this is good or bad, I do foresee a world in which there is diversity in the number of social media sites, and their usage divided along country lines.