Myth #1: Most people came to America for religious liberty. In reality, they were very much fed up with the lack of reform within, specifically, the Anglican Church (at least from a Puritan perspective) and wanted, as Mark Noll puts it, "tighter govermental control of religion than existed in the Old World." [Mark Noll, The Old Religion in the New World: The History of North American Christianity (Grand Rapids: Eerdmans, 2002), 74] They were seeking for purity in the Church and the State and assumed that the solution for that would come by starting over somewhere else and then tightening up that link at the new place. (Now, if you're from an Anabaptist background [i.e. Quaker, Mennonite, Amish, et al], your heritage was concerned with a government that did not dictate religious life. But if you're in a Baptist church today, you may be surprised to know that your lineage doesn't draw directly from the Anabaptists!)
Myth #2: The founders of the US Constitution expected the First Amendment to enforce separation of church and state across the country. In reality, their intention was that this was a state matter and each state should determine what their religious life would look like. They simply did not want the national government to dictate that. In other words, it was assumed that each state would adopt specific religious elements into their makeup. As Noll pointed out (72), 12 of the states then continued to have a religious test required to be taken in order to hold public office.
How does this change or underscore what you've thought about our history and how does it impact your view of the current conditions of our country?