I just ran into the inverse problem. Trying to book an award ticket (domestic US, interisland flight on HA). I live in Canada (and my AAdvantage account address is in Canada) but want to use a US credit card. Even when I ensure that I’m using the US site, it only allows me to input a Canadian address. If I try to change to a US card, it says I have to switch to the US site (which I’m already on), but then when I go back to the booking or create a new booking, it still insists on a Canadian billing address. I’m physically in the US at the moment, FWIW.

However, I input my US credit card and input my Canadian home address as the billing address, and it seems to have gone through, although the ticket just says on request and I don’t see an authorization on my credit card yet.

ETA: ticketed overnight and the charge appeared on the credit card.