Wired Releases Full Text of AT&T NSA Document
So yeah, they are tapping into pretty much all of the US-based internet.
Not necessarily. Unless ATT is actually controlling the shared switch fabric of the exchanges, they can only monitor traffic flowing inside their own AS. Also, there are 5 to 8 major backbone providers who have peering agreements with each other. They generally don't offer transit to each other, so if the source and destination IP is not advertised by ATT it won't go through ATT territory.