This is one area where AA is extremely stingy, even more so than the Star Alliance carriers in the US. AA elites are refused access to any OW lounge when travelling on an entirely domestic itinerary in the North America/Caribbean region.

In *A, a UA/US/CO elite is also refused access, but only to a UA/US/CO lounge. If I can get to a Lufthansa or Singapore Airlines lounge with my short haul economy domestic BP, my *A gold card is supposed to get me in.

(I've always found this so weird. As a top elite on UA, I can buy a full-fare first class transcon ticket and get no access. But a mid-tier elite with Lufthansa can buy a bargain-basement short-haul ticket and get in. Go figure.)