This is excessively tight. IMO there's a good chance you will miss your AA flight, what with disembarkation, going downstairs to the interterminal train, taking the train, going through passport control and trekking out to the assigned gate - and unless things have changed interact with AA security personnel. Of course, the flight began boarding 45 minutes prior to departure.

Fortunately, AA will honor your ticket regardless of whether they are separate or not, but you may have to wait a day or two to fly home (dependent on availability).

If you can change to an earlier flight, you'll save yourself some stress.