That question has served a variety of political causes since July 4, 1776, from legalizing persecution and aiding runaway slaves to fighting Nazis and Communists.
The scholars below have spent years reflecting on the intersection of American religion and nationalism. Their answers to the question invite us to examine the motivations behind the controversy: Why do so many people think the country's Christian history is so important?
If we are talking about 13 colonies belonging to the British Empire, whose king presided over an imperial church, then yes, British citizens residing in those colonies lived under Christian rule.
Those colonies were founded as outposts of a Christian nation. With American independence, however, the British monarchy lost control over its American subjects. Champions of American liberty then celebrated their religious as well as political independence.
In the popular pamphlet some historians credit with overcoming American hesitance about severing ties with Britain, "Common Sense," Thomas Paine cheered freedom from the "degradation and lessening of ourselves" under British rule, proclaiming "monarchy in every instance" to be "the Popery of government."
Hostile to the political theology of both the Catholic Church and Protestant kings, Paine celebrated a vision for America that reflected the democratic god of nature and reason.
Paine was more outspoken and less diplomatic in his religious skepticism than others.
Most notably, Thomas Jefferson sought common ground with Baptists who resented government establishment of religion. And Jefferson contributed voluntarily to his local parish after Virginia law no longer required him to do so, even though his own philosophic views were closer to atheism than Paine's.
Jefferson explained his support for religious freedom in practical terms: "(I)t does me no injury for my neighbor to believe in twenty gods or no God. It neither picks my pocket nor breaks my leg."
Outside New England, American churches at the time of the founding of the United States were relatively small and few in number, and many clerics were at least ambivalent about cutting ties with Britain.