There's no leverage needed, unless you're thinking that the NSA would rather send G-men to disappear the senior staff or something, instead of simply getting a FISA warrant for the hopefully-rare cases where Facebook has reason to push back against an NSL. But Facebook has always claimed they will comply with the law, and the law is very much slanted to the U.S. already, there's not much extra leverage needed.
NSA is undoubtedly not even the only source of these requests either (e.g. many might come from FBI investigating purely "home-grown" extremists, local cops following up on Amber Alerts, etc.), and the non-NSA ones would already have had an Article III warrant issued, which Facebook has always claimed they will obey.
From their FAQ: "The vast majority of these requests relate to criminal cases, such as robberies or kidnappings." and "The report contains the total number of requests we've received from each government, including both criminal and national security requests."
However, even if we ignore all that other nations have their own forms of leverage... it would certainly be easier to unilaterally block Facebook in other countries than in the U.S., for instance.
NSA is undoubtedly not even the only source of these requests either (e.g. many might come from FBI investigating purely "home-grown" extremists, local cops following up on Amber Alerts, etc.), and the non-NSA ones would already have had an Article III warrant issued, which Facebook has always claimed they will obey.
From their FAQ: "The vast majority of these requests relate to criminal cases, such as robberies or kidnappings." and "The report contains the total number of requests we've received from each government, including both criminal and national security requests."
However, even if we ignore all that other nations have their own forms of leverage... it would certainly be easier to unilaterally block Facebook in other countries than in the U.S., for instance.