This is so interesting because the OP had a confirmed ticket with the onward flight to a country other than the country of origin with AA. When I did LAX-PVG-LAX but then had a separate ticket PVG-ICN-PVG, that took a bit of convincing that I was transiting at PVG (<24 hour stay) because it was a separate ticket.

A few years earlier, I flew LAX-HND-SGN on NH. At the LAX check-in, they were concerned about the VOA set-up with Vietnam and finally accepted with me signing some sort of agreement that I would accept responsibility for denied entry in Vietnam, i.e., transporting myself back to HND.

Is such an option not available to AA? Or is it more than cost of return travel and incurring fines, etc.?