Do the VC-25 aircraft used for Air Force One carry missiles to protect itself and its passengers?
If so, can these missiles be fired at potential threats?
Following this source, the armament is "none".
An aircraft so big looks more like like a bomber, and large bombers in these days tend to rely on the escorting fighter aircraft to defend them. On board self-defence weapons of the bomber are not efficient, see this answer. I think VC-25 just does the same.