I've never defined myself by nationality or heritage unless specifically questioned on it. In that case, I would state that I am primarily English, Irish, and Scottish, with a smidgeon of Dutch and Cherokee. None of those ancestries hold significance to me.
When prompted for a description of myself, I typically begin with education status, followed by activities and hobbies, and ending with personality traits and philosophical positions held. For example: Student at UCF, Psychology major, photographer, libertarian, inquisitive.
The description provided to others is strictly for their information, so I focus on what is objectively verifiable. I am more subjective in description when assessing myself alone and tend to ignore anything but traits, which are the only relative constants. I will graduate, my interest in photography waxes and wanes (as all interests do), and my philosophical positions are constantly refined based upon new evidence and thoughts. Traits such as inquisitiveness have always been firmly attached to my identity, as far as memory serves, and they are fully internalized.