I’ve lived here 20 years now and in my experience, it’s largely two, somewhat interrelated, things.
First, the levels of religious belief. This has been commented on by many of us here and written about in books by much wiser people than me, so I won’t retread it all, but in the US the grifters and the right wing have figured out how to play these rubes with the same tricks they’ve borrowed from the churches. The line from Televangeleist to White Power web forums is a straight-line continuum.
Secondly, it’s resentment of others and the childish reaction to want to destroy things if you can’t have them and to deny them others. All their lives Americans are told they live in the greatest country in the world and everyone wants to be like us. I was actually a bit shocked when I found out my kids were getting told this in kindergarten. I’m getting the sense that it is starting to wane a little as the world globalizes and people get educated (part of the reason globalization and education is an anathema to conservatives) but it still prevails especially in rural/ poor areas. “Hey kid, we both know that your gonna spend your whole life in Shitkicker, West Virginia, but don’t forget you live in the greatest country on earth and god loves ya”
They see other people ‘living their best lives’ making positive choices for themselves and having fun and they just want to destroy them because they can’t have any of that. The truth is, a great many could, but they’re deliberately held back by those who profit off the anger, divisiveness and misery (and here we are back at religion)