Actually, the Snowden files show that is happening for non-US Citizens/US-persons.
The NSA only has the legal obligation to obtain warrents for US Citizens not for anyone else. The NSA is unlikely to get involved in civil legal disputes but yes, it can go in and ask for Kafka's data from Google if he is living in, say, Germany.
Even for that there is a due process requirement, contained in E.O. 12333. Obviously the requirements are far lower but even there a random NSA analyst can't simply ask for the data, they'd have to get a supervisor within NSA to approve sending that request outside the agency.
But on the other hand I've not seen evidence that Google simply sells information on specific individuals or otherwise gives it away without that legal mandate.
The NSA only has the legal obligation to obtain warrents for US Citizens not for anyone else. The NSA is unlikely to get involved in civil legal disputes but yes, it can go in and ask for Kafka's data from Google if he is living in, say, Germany.