You are well above MCT. If this were offered as the original connection, I would unhesitatingly book it unless I could not move at a normal pace.
Unlike the UK, there are no formalities of any kind between gates. You simply step off aircraft
#1 and follow the route to aircraft
#2 . No additional checkpoints, Flight Connections or the like.
It is close to impossible to predict specific gates at DFW as those are constantly changed, but, even if you are the last person off your inbound and are at the most remote AA international departure gate capable of handling your aircraft, you will be at that gate in 20 minutes. The SkyLink Tram operates outside (on the sterile side) of security.
If there are delays, the difference between 1:20 and 1:45 is not so great that it will make a significant difference and DFW is centrally located with multiple options on BA/AA back to the UK.