To say that [the revival of evangelical Christianity in the 1820s] marked a turn away from the spirit of the nation’s founding is to wildly understate the case. The United States was founded during the most secular era in American history, either before or since. In the late eighteenth century, church membership was low, and anticlerical feeling was high. It is no accident that the Constitution does not mention God….
The United States was not founded as a Christian nation. The Constitution prohibits religious tests for officeholders. The Bill of Rights forbids the federal government from establishing a religion, James Madison having argued that to establish a religion would be “to foster in those who still reject it, a suspicion that its friends are too conscious of its fallacies to trust it to its own merits.”—Jill Lepore, These Truths: A History of the United States (2018), pp. 199-200