2.20 should be plenty of time to clear immigration and security at DFW. That being said, the chances of a schedule change on the DFW-ATL flight between now and then are high. I would book the cheaper flight and then wait for a schedule change to see if you can get a longer connection, if it would make you feel more comfortable. If a schedule change never happens, you should still be fine with that original flight schedule and even if you somehow miss the onward flight due to a customs delay, AA will recommodate you on a later flight.