I read the OP as saying the original itinerary was BWI-LHR-CDG on BA, and that’s now been changed to DCA-JFK-CDG on AA. And the worry is not making the connection in JFK. 2.5 hours really should be fine. As said above, if massively late you may well get auto rebooked so keep checking app. If not if just go to an AA desk in the concourse or in a lounge and they’ll re-rebook you, most likely onto a connection via LHR! But 99% chance you’ll make your connection.