If you are traveling first or business class, you get access to any oneworld lounge at that airport on that day before that flight.

You will get off a domestic AA flight in Terminal 4. Because there are no customs from a domestic flight, you will be in the terminal with all the departing pax. If you go to the Admirals Club with your biz or first boarding pass, you technically can enter, even though the flight departs out of the bradley terminal.

First, this is assuming you have a boarding pass. Second, this is assuming that they follow the rules, which they don't always do.