This matters if you're an AAdvantage member. Your profile doesn't say that you are. If you expect to fly BR (don't ask me how they came up with that code) a lot, you might want to join their Evergreen Club.

Or, you might look into what other partnerships and/or codeshares they have in case one of them is more useful to you than AA miles. (Unfortunately, Star Alliance bases credit on the operating carrier, as opposed to OW which bases it on the carrier whose flight code is on your ticket, so getting UA credit might not be possible even if you find a *A code-share.)

A third option would be to find another airline, ideally a *A member, that flies to wherever for a reasonable fare - but you've probably already tried that.