The risk outweighs the benefit. We can't really know the extent that foreign countries interfere with our elections or sow racial unrest in our country. Furthermore social media has already been used to locate and target military personnel.
Enemies can use social media to not only inexpensively find and target NATO forces — but also manipulate them, new research has concluded
www.google.com
Countries use exercise apps with Google maps to locate undisclosed military bases, and to generate target lists of personnel in case of a war, both people they may want to kill or blackmail.
Even if so much information wasn't public all you need to do is hack an exercise app like strava and start looking for locations where there is a lot of users compared to population size and uou can find most likely where undisclosed military bases are. Sure you can forbid military personnel from using it but that requires an incredible amount of effort and you won't hit anywhere near 100% compliance.
Social media is a goldmine for intelligence agencies. There is little reason for the average person to be on the same internet as China, India or Russia, it provides tons of opportunity for scammers and foreign intelligence agencies for virtually no benefit to the average person.
There have been numerous occasions where countries have engaged in serious cyber warfare up to the point of knocking out every computer that runs windows in a smaller country simultaneously. There is huge risk to having a global internet system, the only reason we still have it is because most of the victims have been smaller countries like Ukraine.
If you at least make sure that hackers have to physically be in the US you raise the costs significantly and increase the chances they can be caught. It's also kind of comical that we are on the same internet as countries that won't extradite their hackers to the US. There is no good argument for that being the case.