There are no differences, both in practice and in theory, to the privacy rights of citizens and non-citizens. Everyone is spied on, and it is legal. The NSA is tasked with spying on foreign nationals. The FBI is tasked with spying on US nationals. Everyone seems to be getting caught up with these legal technicalities. Our agencies spy on everyone they can (as probably does every spy agency in the world). Our government might not even be aware of or in control of it.