Identity crisis?

Since I've been in Singapore, so many people have tried to guess my ethnicity and I think I've been asked if I was every asian nationality. Here's a list of countries people think I'm from:

- Malaysia
- Cambodia
- Indonesia
- Japan
- Korea
- China

I think most people have asked me if I'm Korean, which surprises me cause I have never been assumed to be Korean in the US. It's mostly when I travel out of Singapore when people start guessing I'm from Japan or Korea. I've come to respond to these ethnicity questions with "I'm American, but I'm Chinese." Which isn't too definitive in and of itself (my roommate laughs when I use this response), but I guess neither are the ethnic and cultural identities I personally identify with.