Well, why call that out in a hypothetical if it's not a difference? If GP had called out the hypothetical Asian student's height or weight or video game preference but not the hypothetical black student's, I would have assumed that was significantly different as well.

There's no way you seriously used the existence of a rich black family in the same locale as an asian as evidence that it wasn't in the US.

Indeed, there is no way that I did that. GP specified that one of the two was American, and didn't specify that the other was, so I assumed it was a relevant difference.