As said, USDM will likely continue in its current incarnation for the time being as far as can be seen, except now with oneworld carriers instead of Star Alliance (barring the short term agreements with some Star Alliance carriers).
Redemptions with AA are not as generous as USDM - no stopovers allowed (unless going through North America, when one stopover allowed at the international gateway), routings must be reasonably direct (needs to be a published routing and MPM+25% enforced strongly), fixed dictated rules of which zones or ports may be transited in the cases of interzonal travel that may span across more than one zone.
On the other hand, AA awards are booked as one-ways rather than enforcing a return journey, so open jaws are easy to create (you can even have double open jaw if you wish). AA also has the oneworld Explorer awards which can cost a bit but depending on routing can be very lucrative with as many stopovers as you can fit in the ticket.