As a former AA employee until last year, I’m not aware of any system-wide climate control policy. Depending on the aircraft, the climate can be controlled either directly at a flight attendant station or from the flight deck. In either case, the cabin crew are usually the ones who control the temp, either directly or by calling the flight deck and asking for an adjustment.

One difference would be when connected to the PCA unit on the ground (the yellow duct that goes from the unit on the jetbridge to the plane to supply conditioned air). There isn’t a way for these units to sense the temperature in the cabin so when they are running, they simply supply air at a constant rate and temperature. During the winter (supplying warm air) this can make the cabin quite stifling. I don’t know if that has anything to do with your experience or not.