I bought business seats AA18/177 SFO-JFK-SFO; however AA177 was only available on a higher fare class, so I bought US177 instead.

When I go onto the AA site to manage my booking, I can do everything (edit my Secure ID, FF info, pre-choose my entrées) except select seats on the return flight (AA177). I have separate AA and US confirmation codes, so I logged onto the US site thinking I could do it there, but no dice; I'm directed to go to the AA site to choose seats.

Am I doing something wrong or is this a system issue?