This historian writes:
"Episcopalian, Methodist, Presbyterian, Lutheranâ€”the name hardly matters anymore. The average American these days would have Âtrouble recalling the dogmas that once defined all the jarring individual sects, but their names remain at least half alive: a kind of verbal remembrance of the nationâ€™s religious history.
Before the 20th century every denomination fought each other to acheive victory as the nationâ€™s legally established church. The Baptists fought it where they feared it would be the Episcopalians, and the Episcopalians fought it where they feared it would be the Congregationalists. The oddity of American religion produced the oddity of American religious Âfreedom.
So he says since no church could take over things are evolving into relativism (where there are no denominations, doctrines and creeds do not matter). https://www.firstthings.com/article/2008/08/001-the-death-of-protestant-america-a-political-theory-of-the-protestant-mainline