Just asked husband in the beginning of our 1st domestic AA flights we booked, we had trouble. We ended up booking 12 domestic eventually. We were IN Argentina at the time. He thinks he used our VPN set to United States ( our home country). Ok, now he says he also remembers going to the Argentinian site, and choosing from dropdown menu home country. But going thru the spanish language site to start.

I'm sure you have tried all of this, but???

We spent months in Argentina in 2022 and some in 2023, so if you have any other questions, just ask.