Over the last 2 months BA193 has been 43% on time with an average 35 min delay, and as AA1211 is the last flight to CUN, this is not a connection I would want to make!

On the positive side, if the BA flight is late arriving you will probably be met by someone with a priority pass to get through immigration (I think they do that in DFW?).

But I would try to get moved to the earlier BA flight. Could be difficult to do, but should be allowed if there is (even a minor) schedule change to either flight. I would also double check your flight times, as for much of the year AA1211 departs at 16:55, which would make your connection invalid.