Apparently, we're not so different on our perspectives, after all.

Yes, a stranger striking up a conversation with you that begins with your ethnic heritage is at least suspicious. Even threatening.

If, on the other hand, the same stranger happened to strike up a conversation with you, and the two of you found that you were hitting it off well and the conversation was a little more in-depth, and you found that you might want to get together in the future, a question about your ethnic heritage might be appropriate. Although it would probably follow more relevant questions, like where you live, what you do for a living, etc.

Regarding the Native Americans, I realize they probably crossed an isthmus that once existed between what is now Alaska and Russia, but really, if you're going to be that particular about where everyone's from, you're going to trace us all back to our respective Cradles of Civilization.