It is the case that AA doesn't book into Iberia. I don't know why, it does plenty of other airlines, including quite a few non oneworld airlines, but not Iberia. I don't know why. And I can see why BA wouldn't sell it when they have their own codeshares on the some/all the sectors.

So I'd give IB a call. You probably can get Iberia.com to give you an interesting price for DUB-CLT and back, if that helps, or you could try the Spanish language version of Iberia.com, if you have some schoolboy/girl Spanish to fall back on. I haven't tested it out on this schedule but it is often one step ahead of the English website.