Harold Bloom's observations from 1992: I believe his premise that the Protestant heresies, which Frederick Kinsman, an ex-Episcopal bishop of Delaware who became a Catholic (Reveries of a Hermit is a series of talks he gave at Notre Dame University in the '30s), rightly said began with emotion-driven, inconsistent, partially Catholic Luther's appeal to private judgment, have turned into the American religion; they ultimately mean self-worship. (Reinventing yourself, a distortion of being born again, fits into that, so Bruce Jenner still claims to be a good Christian, God's giving him XY chromosomes notwithstanding. America thinks it makes all things new.) Feel-good pietism (Bloom notes that real Christian writers, as in old Europe, warn against confusing feeling with truth or grace); the Inner Light; Jesus and me; I don't need a church. Related: moralistic therapeutic deism, except unlike deism, in the American religion God definitely loves you, peer to peer, a distortion of a couple of truths, including the Incarnation (Jesus is true God and true man). (Me: liberal high church, Episcopalianism, really says the trappings of the church are nice and fun but ultimately not necessary.) But the Mormons, whom he respects partly for their founders' genius and sees as quintessentially part of the American religion (a home-grown new religion), are a strong community (me: people convert and stay for that, not the theology). But while all Protestantism lends itself to the American religion, I don't buy Bloom's argument that the Southern Baptist Convention, while non-credal and individualistic, is full-on American like the Mormons and New Agers in believing that man is eternal, part of an eternal universe and thus every man is really a god. (He considers fundamentalism, which he doesn't like, part of the American religion just like New Age.) In the tradition of Mark Twain, who rubbished the Mormons, Bloom also takes fun swipes at Christian Science and Seventh-Day Adventism (cults started by boring, rather dim women). Bloom's also a fan of Ronald Knox's Enthusiasm. He agrees with the line that Europeans know what Christianity is and most now definitely reject it; most Americans are still religious, thinking they're Christian but they really aren't anymore. (Unspoken belief: Universalism? Of course! I'm a god!)
Also from Kinsman: Calvin's Geneva, where disobedient children were beheaded, was the ISIS of its day. Reminds me of the idea I read somewhere that in the event of a Muslim conquest, the evangelicals could be flipped into being good Muslims, like the Bosnian Bogomils were. Interesting, though it may just be a liberal Protestant and secular (sons of Protestantism) putdown of their conservative brethren against whom they're fighting the culture war. Bloom: Mormonism in its true form from Joseph Smith, Brigham Young et al., is as different from Christianity as Islam is, neither Christian nor conservative. I'm fascinated by Bloom's noting how much Smith's new religion resembles not only Gnosticism but Kabbalah; either Smith had unlikely, unknown access to books hard to find then or he was so smart he managed to parallel those things on his own. There really is nothing new under the sun.
I think in Bloom's overview of America, the Eastern Orthodox theologically and sociologically would be what they are, Catholics without the Pope, but you can argue that the self-reinvention of the convertodox (consumer religion, religion as lifestyle accessory) fits into the American religion, which often appropriates Christian trappings (why the Mormons have you thinking they're just a kind of conservative Protestant, a mask they adopted to fit in). Franciszek Hodur (really a liberal who'd have been at home in liberation theology and Call to Action) and his Polish National Catholics were/are definitely part of the American religion (lots of their clergy are Masons, like Protestant ministers), even if many parishioners don't know it (at the parish level, at its best it's congregational Tridentine Catholicism); like the Mormons, hiding behind a cultural conservatism (the trappings of Polish Catholicism).
Bloom: in the American spiritual hothouse, in which the first big religious revival was orgiastic and like the Pentecostals many years later, Catholicism is relatively sedate!