How would you break up Facebook?
Before the US Rockefeller empire was broken up there was already legitimate competition oversees. It's just a less scalable business model. In Facebook's case, it is directly beneficial to have your US, European, and Asian friends all using the same medium.
The natural "equilibrium" size of a global monopoly has, and will continue to, increase as the world becomes more interconnected. If the point of regulation is to protect the consumer, breaking up Facebook wouldn't achieve that. I think what makes regulating these companies so difficult is that consumers truly benefit from the abuses they commit. One of social medias greatest accomplishments is giving normal people a big voice, how do you simultaneously nurture that and prevent the spread of miss-information?