Timon Cline has offered a very good piece at The American Reformer on the Protestant foundation of the states that formed the American Union in 1788. It’s a worthwhile piece that touches on a broad range of historical realities in the Early Republic. Cline understandably pushes back at the overstatement of supposedly secular origins of the American republic. “The sects and factions that dominated the socio-political life of the early republic were predominantly of Reformation heritage.” The theological commitments of the Revolutionary generation, “for better or worse, conditioned the early character and trajectory of the nation” and Cline supposes their theological suppositions to have been Protestant. He concludes by arguing that “secularist pluralism has no place in the historic, American errand into the wilderness. And until we recognize this, we might toil in the wilderness forever.”
The Christian socio-civil foundations of the United States seem historically incontrovertible. My main addendum would be to note that secular pluralism, or what might be more accurately described as the right to be irreligious (but not necessarily anti-religious) also has a time-honored and legally protected place in American civil life, and should continue to have that place. In the Nineteenth Century Presbyterian divines rightly celebrated the Protestant foundation of the United States but they understood that Protestantism guaranteed freedom. The federal union was never meant to create a secular state or states, but it also was not mean to create a specific type of religious citizenry.
In an 1852 sermon, the pastor of Pittsburgh’s First Presbyterian Church, Nathaniel West, proposed that the United States was indeed a Protestant nation. God had appointed the republic to be the new protective Protestant “Ark of God.” The very name Protestant, said West, “associates with it whatever is held sacred as to genuine religion and civil liberty.” Pure religion, and well-regulated civil liberty were “the strong instrumental arms of sure protection to a nation. Where they are, God is, and where he is, there spiritual and temporal salvation are.” Religion and civil liberty were all any nation required for “safety and prosperity.” “Give these two blessings to any people, and they must flourish. Take them away, and all that is debasing, demoralizing, and enslaving, must follow.”
West listed the denominations he believed bore testimony against Roman Catholic tyranny. His list was ecumenical but nonetheless still Protestant. He denominated Lutherans, the Church of England, Scottish Presbyterians, Methodists, and various other Protestant sects as friends of God’s Ark—the United States—but also noted that there were enemies to the Ark as well. “With the Ark,” West exclaimed, “is associated every thing sacred and venerable, in religion and civil liberty. All who remain under the blinding prejudices of Judaism—all Pagans, Mohammedans, and Infidels, are enemies to God’s Ark.”
Religious historians and political scientists rightly push back against the notion of a de-churched, de-Christianized, and anti-religious advent for the United States. Yet the Protestant Founders—fifty-two of the fifty-five signers of the Declaration of Independence were Protestants, as were the majority of the Constitution’s signers—rejected religious tests to sustain a specific type of religiosity. This rejection was not to actualize en masse secularism, but to establish a broad-based religious order that included Jews, Catholics, Muslims, and others. Their inclusion nonetheless rested on the Anglo-Protestant foundation of civil liberty. The United States’ religious order would understandably be more than Protestant, but it would never be anything less than Protestant either.
 Nathaniel West, The Ark of God: The Safe-guard of the Nation. A Discourse in Defense of Protestantism (Pittsburgh: J.T. Shyrock, 1852).