Today's flight was operated by N127AA. Unfortunately the most recent photos I can find date back to June this year. They certainly don't show any indication of ETOPS on the exterior paintwork. Perhaps, as Dave R suggests, it is a very recent addition.
J.O. said:
American never purchased the narrow body Airbus - all of them are former USAir / America West fins.
According to Airbus the order was signed by AMERICAN AIRLINES July 20th, 2011.