I find DFW immigration is not too bad, and the airport itself is very efficient for connections. On a single ticket I would have no problems with a 2h20 connection. I have done such connections in the past (I do not have a Green Card, Global Entry, or so on though I am ESTA-eligible so I can use the kiosks). Use the Airtrain to get from to your next flight after you clear Immigration, Customs and security screening, don't try to walk across the airport on a tight connection (in case you were tempted to do so).
If you do miss the connection then AA will rebook you, they are very efficient about it and if necessary may well put you on another carrier. I am willing to rely on AA rebooking me successfully within a few hours on a route with 5 flights each day (and several other possible routings via other airports).