Here's why wiretapping allies is important: if the US agencies can wiretap you, then so can Russia, China, Israel, North Korea, etc. So if you notice your allies being sloppy with their InfoSec, you can also let them know about it before the enemies find out and exploit them.
So it's your job to implement security that nobody else can tap. That's why citizens pay taxes to the defense sector, that's why you have intelligence and counter intelligence agencies, etc. they just need to do their fucking job instead of going after citizens who buy weed online or who call politicians dicks on Xitter.