Stroller on board? I echo those who said that either the gate attendant or at minimum, the flight attendant at the entrance to the aircraft, should have caught that upon boarding and mentioned something.
I fly AA almost all the time within the US, simply because I don't have really any other choice. Generally haven't had too bad an experience with the former US-Airways operations; the former AA flight I took a few weeks ago was unpleasant though (pretty sure the 737 was as old as I am).
People just need to learn to pack less and more efficiently.
