That's obviously a really exaggerated example (although I definitely agree there are clueless people who act like that guy), but notice when he first asks her where she's from...

He bookends it with a backhanded compliment about how impressed he is with her English.

These are the types of microaggressions that "othered" people endure over their lifetimes like thousands of cuts.

When it's usually preceded by something as seemingly neutral as "Where are you from?" -- I can understand how that would be a red alert causing one's antennae to go up.