The models are complex and get data from many sources. If we assume they really do believe you live in the US, then it's odd for you to suddenly pop up and want a credit card with no other credit. Students get credit cards b/c they are student age and fit a risk model. It sounds like you're older.

Is your name on any of the house items like utility bills, deeds, etc...? Where do you pay taxes? How do you pay for things while living outside the US? Are you employed by a US company?

Keep in mind the people you speak to on the phone have no idea what goes into the model. They mostly read the same score/rejection that you do. My guess is the model is picking up signals you aren't in the US and that's causing the rejection.