I'm also very curious, and I'm sure I've asked foreigners where they're from. I'd never ask that of someone who spoke with an American accent though. I assume they're from here. To assume otherwise merely because they look Asian or something is just rude IMO.

My sister introduced me to the word 'xenophilia' - the opposite of 'xenophobia.' I think I'm a xenophile. I'm just drawn to foreigners. I remember in my first week of university (I came from this tiny, all-white Kansas town), I saw this swarthy-looking guy in class and immediately buttonholed him and asked him all about his country (Pakistan) and tribe (the Afridi). After we'd been talking for about an hour, he told me I was the first female he's ever talked to who wasn't his relative. And he was like 20 years old! I hope I left him with a good impression of my gender.

I suspect part of his problem is he has huge issues around race. Also, his dad abandoned him. So, these questions are inherently painful for him.