Nonetheless, one of two things is true: 1) the U.S. actually threatened Germany that it would refrain from notifying them of terrorist plots against German citizens and thus deliberately leave them vulnerable to violent attacks, or 2) some combination of high officials from the U.S. and/or German governments are invoking such fictitious threats in order to manipulate and scare the German public into believing that asylum for Snowden will endanger their lives. Both are obviously noteworthy, though it’s hard to say which is worse.
I’ll be honest, I’m a little skeptical that an overt threat like this would come from the highest office here in the US, but I wouldn’t put it past some senior ranking US intelligence official to make a veiled comment to a German counterpart. Friends won’t be friends when it matters if threats like that are being made. Whether or not I agree or disagree with what Snowden did, that whole thing was a giant black eye for US intelligence agencies, and they probably want to keep Snowden holed up where he is. 
Unless they can bring him back here ↩