Specifically, the GOP fearmongers most. The Dems are much more internationally & diplomatically inclined when compared to their political opponents.
Tinfoil Hat Time: I think the separatism in the US is being stoked by outside forces. If you read a summary of The Foundations of Geopolitics it sounds very familiar to what’s happening. I also think Social Media needs to go, or rather engagement driven algorithms, because they create informational bubbles that polarize society.