some Norad interceptors are part of the air national guard of Massachusetts and Alaska.
NORAD also has a good band, the NORAD commanders.
But the media doesn't really have to be right on this. IF it was over the USA (atlanta is still in the USA isn't it?) then it was likely the USAF. I would be surprised if it were not.
AS to bomb threats, what could an interceptor do? WELL< if the the plane blew up, it could report such.
IF a bomb went off and the plane was still flying , the interceptors could assist in assessing damage and controlability issues. Aid in navigation (follow me), and utilize hand signals instead of radio if the electrical system was damaged.
So. They might not shoot it down. Unless the plane became a hazard to the population at large.