A question on the Britain attacks

The NSA operates a massive foreign surveillance effort, supposedly capable of sucking up and analyzing vast amounts of telecom, fax, email, etc.

Outside the US, these efforts operate largely without restriction.

So, how is it that there have been multiple incidents coming out of Muslim communities in Britain, Spain, etc, and the US has seemingly not issued a single warning?

(And, what promise does that offer for similar unrestricted monitoring here in the US?)