The author's theory is that Americans, in particular, are inclined to find their own realities. I'm not sure it's Martin Luther's fault, despite his claim that people should be able to read the Bible in their own language, but regardless, after the Reformation various sects developed, some of which wound up in what became the U.S. This is where the real craziness started; there were plenty of Protestants in Europe by the 17th Century but they weren't as nuts as the ones who settled in the New World.
What the Puritans, the Pilgrims and the sects that came later had in common was a rejection of the conventional theology of the Church of England and a whole lot of weirdness involving supernatural beliefs in witches and demons. There weren't a lot of countervailing traditional religions to tamp down the weirdness. People were already disposed to believe in the supernatural; then along came the Mormons, various snake handling churches and speakers in tongues. During the early 20th century there were proto-televangelists like Aimee Semple McPherson, believers in spirits, seances and ouija boards, and illusionists like Houdini.
Fast-forward to the late '60s and you get LSD and peyote, Carlos Castaneda, the notion that whatever you wanted to believe was real, plus crystals and other non- (or anti-) scientific woo on the Left, while at the same time the evangelical Christians with increasingly off-the-wall theologies were gaining popularity on the Right. Other fantasies were being fulfilled by Disneyland, cosplay, theme parks, and other activities that allowed people to step away from reality. The central principle is that American society encourages the notion there is no absolute truth and no scientific proof you can rely on. If you don't want to "believe" in climate change, or God, or vaccinations, you don't have to. So, when Trump finally turns up, a lot of people are ready to believe bald-faced lies because there is no real truth.
It's a very thought-provoking book.
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