- last post: 01.01.0001 12:00 AM PDT
She is a chip-embedded personality extracted from a flash clone of Dr. Halsey (the woman who sorted all the spartans in their training).
Whatever Halsey's nationality is, that is what cortana is.
And you are also forgetting that when cortana was created, there were many non-earth human planets, and so she sould be a currently unknown nationality.