JDiver

Your flight is operated by American Airlines - you must check in at the AA counter. If you go to Iberia, they will only send you to the American counter.

I've flown AA and IB for many years, including codeshares, but the idea is to check in with the operating airline, whichever airline is actually flying the airplane.

I doubt you will be able to check in online - but it's possible. Try and see what happens. Codeshares have their positive attributes - they are often cheaper, for one; they also have their minuses - it's often a challenge to get seat assignments on the operating airline's aircraft until the day of flight, for example.

It's sometimes also difficult to get the selling / marketing airline to accept responsibility for the operating airline's delays, and sometimes they can seem to be dumping blame on each other.