North or South?

I went out for karaoke with some friends at this local favorite Otani's. It's a Japanese sushi house that hasn't been touched since the 70's. The friends that gather there are a mixed bag of Asians, WASPS, Black what have you. I was sitting next to my long time friend Arnell and this other white girl whom I'd never met before. We were chatting a little bit and she asked me, "What kind of Asian are you?". In my head I wanted to just get up and walk away. After nearly 30 years of this shit it tires on you. I was polite because I assumed she was a good friend of someone there or else why would she be sitting at our table? I politely told her I was Korean then she asked the Kicker.  

"North Or South?" 

Seriously? I looked her dead in the face to see if she was snickering as some sort of tasteless asshole joke (which would of been better) but no she was genuinely asking as if she had no practical clue. I was so insulted at her ignorance I couldn't even answer, I pretended to be drunk and got up to catch some friends going outside for a smoke. There was no way I could of answered that question politely. I told my friends outside what was said and they of course burst out laughing, and gave me a little background on the unfortunate girl. She wasn't very close to any of them just came because she knew the group was always there and kind of settled herself into it. Her husband is in the Army which I found a little frightening. I hope that he is better educated then she is but if not what kind of uneducated people are we sending out internationally to represent the United States? That is just a whole different bag of tricks to talk about.

Let's get back to her question, "North or South". There are several levels of offense here. Firstly at my age if I was from North Korea would I even know English especially when I completely lack an accent? How in the sam hell would I end up in Columbus, Ohio at a Japanese restaurant (Japanese of all things (seriously I have nothing against them it's just the history)). Also if she seriously thought I was possibly from North Korea does she think I am pushing into my 60's or something? I know plenty of older Koreans who were originally North Koreans before the war, who moved to the south, or moved out of the country but they would be about my parents age and only a little younger. My dad just turned 70 and my mom is 68 I'm only 30 and the war started in the 1950's. Just trying to do the math is ridiculous, just like her question.

If you were seriously posed this question out in public how would you handle it?