I have an Irish surname despite having never been to the island in my life. What would you call it if I was leading a division of the Irish army to try and retake Derry?
May be true, but generally Americans outside of a few backwater racist areas will consider it valid to refer to someone as an 'American' if they were born here, unless they renounced citizenship. And doubly so if they were born here and spent the vast majority of their childhood here.