Sometimes there is a legal definition. Sometimes there is a - often racially influenced - folk definition. There are, of course, others between and perhaps beyond these.
If any manage to exclude you, there’s your answer.
That doesn’t necessarily mean that they’re right, of course, but some hold more weight than others.
Nationality is a somewhat nebulous concept.
Sometimes there is a legal definition. Sometimes there is a - often racially influenced - folk definition. There are, of course, others between and perhaps beyond these.
If any manage to exclude you, there’s your answer.
That doesn’t necessarily mean that they’re right, of course, but some hold more weight than others.
Edits: Improvements