Apple Credit Card "Verify Your Identity"

I wanted to apply for Apple Credit Card from my iPhone. One of the required fields while signing up was "Verify Your Identity" it asked me for the last 4 of my SSN and Citizenship. I have a SSN and have lived in California most of my life but was born in Mexico. I have a state ID and work permit.

I called 800MYAPPLE and asked one of the reps, she told me to put United States but just to make sure I called an apple store and they transferred me twice to another rep and she said put Mexico.

I am very confused as to what I should put in this field?