For US passport holders without checked luggage, 2 hours is generally a safe connection from TBIT Int'l arrival to T4 domestic departure. For foreign passport holders, 2 hours is really on the fence especially if you are on two separate tickets. You have to get in the long line to get finger printed which can take 1 hour or longer. But no checked luggage is a big plus... once you clear immigration, you can skip the luggage line and go straight thru custom. You can clear security in TBIT arrival level (see details on page 1 of this thread) or take a short walk to T4 and use the AA elite line, which may be shorter... or much longer. Hard to predict.

But regardless, check in with AA in advance so they know you plan on making to flight.