The religious views of the Founding Fathers are of great interest to propagandists of today’s American right, anxious to push their version of history. Contrary to their view, the fact that the United States was not founded as a Christian nation was early stated in the terms of a treaty with Tripoli, drafted in 1796 under George Washington and signed by John Adams in 1797: 

As the Government of the United States of America is not, in any sense, founded on the Christian religion; as it has in itself no character of enmity against the laws, religion, or tranquillity, of Musselmen; and as the said States never have entered into any war or act of hostility against any Mehomitan nation, it is declared by the parties that no pretext arising from religious opinions shall ever produce an interruption of the harmony existing between the two countries.

The paradox has often been noted that the United States, founded in secularism, is now the most religiose country in Christendom, while England, with an established church headed by its constitutional monarch, is among the least. I am continually asked why this is, and I do not know. I suppose it is possible that England has wearied of religion after an appalling history of inter- faith violence, with Protestants and Catholics alternately gaining the upper hand and systematically murdering the other lot. 

Another suggestion stems from the observation that America is a nation of immigrants. A colleague points out to me that immigrants, uprooted from the stability and comfort of an extended family in Europe, could well have embraced a church as a kind of kin- substitute on alien soil. It is an interesting idea, worth researching further. There is no doubt that many Americans see their own local church as an important unit of identity, which does indeed have some of the attributes of an extended family.

Yet another hypothesis is that the religiosity of America stems paradoxically from the secularism of its constitution. Precisely because America is legally secular, religion has become free enterprise. Rival churches compete for congregations - not least for the fat tithes that they bring - and the competition is waged with all the aggressive hard-sell techniques of the marketplace. What works for soap flakes works for God, and the result is something approaching religious mania among today’s less educated classes. In England, by contrast, religion under the aegis of the established church has become little more than a pleasant social pastime, scarcely recognizable as religious at all. — Richard Dawkins, The God Delusion (P. 39-41)