The NSA are interested in any and all sources of information, and probably collect just as much or more of it from foreign sources than domestic ones.
Yes, the recent media hoopla has been over the NSA collecting information on Americans in America. But that does not mean that the NSA is limited to collecting information in America. Quite the contrary. Historically, they have been more about collecting foreign intelligence abroad (ie. spying on the rest of the world).
This reminds me of a quote: "You have a choice: you can live under US domestic policy or US foreign policy". If you think you're safe or exempt under either of them, you might have some surprises in store for you.