One positive implication will be (at least some) additional airports in the route network For example, AA will (re-)gain service to many Northeast airports that they previously served. (PVD, ALB, SWF, etc). It's nothing like DL gaining a strong Asia network with the NW merger, but there will be added destinations.
Has anyone come across a list of airports that US serves but AA doesn't (and vice versa)? That would interesting to peruse.