If Facebook had EU servers, then they would need access to the data on those servers from the USA. Technically the NSA can still force everything out of Facebook in the USA, I guess.

But this will again be incompatible with EU law. According to the ruling of the CJEU (at least what I understood from it), any company collecting data cannot hand this data over to an entity which is suspected to take part in a system of mass surveillance. Thus, as long as the NSA can reach Facebook's EU servers, it shouldn't legally be possible to have Facebook in the EU.

So I'm really interested in what kind of solutions they will find. If I needed to guess, and the CJEU ruling is the guideline, I'd say that this is a thing that Facebook, Apple, Microsoft, etc. can't really solve by themselves. Rather, the US government needs to take action. There needs to be some agreement.

But, if the EU insists on its stance, that agreement had to be really weird since not even US citizens have that kind of protection from their own secret services.