it's not perfect but go to google flights, select the "Explore Map" view and filter flights for American/One World and non-stop. Then for departure cities just cycle through the AA European gateways (NYC, PHL, CLT, MIA, DFW, ORD, LAX, and RDU) and leave destination blank. (I think that's all of them, but if I missed one someone from FT will point it out). In the map view you will see every city in Europe that AA has a non-stop flight to from that departure city with a red circle over it. You can click on the red circles to get details.

This is what I did to accomplish something very similar to what you want to do.

Taking things to the next level, you can get an expertflyer subscription and search for saaver inventory and set up alerts for any that frees up on your preferred routing.