It is an American thing that arose from, and persists because of how Americans ‘do’ Christianity.
As I said in another post, start with Max Weber, and then explore more of the history of how Christianity and Christian Denominations, cults, sects, revival movements, etc, have shaped the country as a whole, in ways that are distinct from how other kinds of Christianity have shaped other countries in the last 300 or so years.
Like… the whole reason we have the First Amendment, the freedom of religion part… was mainly to make it so that none of the varying Christian Denominations would be able to use the government to censor or outright oppress or murder each other.
Read the journals of the founding fathers, federalist papers, etc, if you doubt that. See how most of them were Deists, who… just believed in a big creator God, but basically no theology of any particular Christian branch… the neutral middle ground.
America was largely initially founded by populations of varying kinds of extreme Christian Sects fleeing persecution in Europe… and a lot of our early history is… those sects persecuting and mistreating, or at best, barely tolerating and competetively trying to proselytize, other sects that just over here now, on a different continent… as well as all the indigenous populations… and the imported slaves.
