Aside from capability, the relationship between the US and European countries is so biased towards the US that, politically, I just don't think they'd risk it.

Aside from capability, the relationship between the US and European countries is so biased towards the US that, politically, I just don't think they'd risk it. The US spies on everyone because they can, and because they have prepared to do basically anything they think might be in their interests; when Germany discovers the US spying on them, what can they really do about it? Whereas if it was the other way, all hell would break loose.