Here is my experience with this.

Im a US citizen that lives overseas for work ( Honduras) for the past 5 years. Since i always purchase my roundtrip with origin SAP to MIA..... my return flight looks like a one-way to AA.

When i wasnt AA gold ----- i used to get crap/questions for this all the time. It got soo bad-- that i started flying TACA instead of AA because TACA never asked/cared....

however i figured out some ways to dodge this issue with AA...

I used the curbside check-in---- normally the guys there didnt asked about additional doc info--

Other times i was lucky and may of had a future ticket already booked, so i showed this as evidence.

One time however a AA agent refused to issue me a boarding pass---- unless i presented Proof of residence in Honduras -- or a return ticket. So I was forced to pay for a refundable one-way ticket.... When arrived in Honduras i went to the AA office and was refunded the money.

Once I became AA gold----- i almost never got asked for any additional paperwork or information.

Immigration never asks for that info---because i guess legally you should have a return ticket.....

Suggest purchasing a refundable one-way ticket back to avoid any problems...