Regions are not not necessarily race either. It could easily be about culture and the associated value systems. For example during WW2 - even before the US join

Regions are not not necessarily race either. It could easily be about culture and the associated value systems. For example during WW2 - even before the US joined it - america did reject refugees from europe because they might have been nazis. Nazis were just as caucasian as most americans, but they had a culture that was clearly seen not just as incompatible but as hostile. To the "alt-right", fundamentalist christians, nationalists or simply less-informed conservatives someone from the middle east may appear to have a similarly fundamentally incompatible value-system as a nazi would have to an american in the 1930s or a commie during the cold war. Race and Nationality are a proxy for religion and culture which is a proxy for value systems. And value systems are what people disagree with and vote against.