In his 2007 book American Gospel: God, the Founding Fathers, and the Making of a Nation, Jon Meacham He argues that America was not founded as a Christian nation, but he also declines to classify it as a purely secular nation where religion must be expunged from the public sphere. In clear, concise language, he relates the role religion played in America from the founding of Jamestown to Ronald Reagan, although he is rather sporadic in his approach, often flying through great expanses of history, including the Great Awakening (a rather strange omission for a book on religion and America). He argues that America has both "public" and "private" religion, the private religion being specific (Christian, Jewish, Muslim, Hindu, etc.), and the public religion being a type of general deism. He concedes that, on the whole, religion has been a positive influence on America.
While I appreciate that he approaches the role of religion with a moderate tone, I'm not sure I find his overall characterization of America or its founding fathers as religiously moderate convincing. Firstly, the founding fathers well may have been moderate for their own day, but they would hardly be considered so in ours. What if a modern President, as Abraham Lincoln once did, suggested that a present war was God's punishment for the national sins committed by Americans? (Indeed, Meacham himself, in the pages of American Gospel, reacts in horror at Jerry Falwell's extremism for suggesting our national sufferings in 9/11 were the consequence of our national sins.) What if a modern president where to make the kind of religious proclamations, today, that past presidents once made without concern that the public would scream, "Separation of church and state"? George Bush nearly sent people into fits merely by using words like "good" and "evil," but "moderate" politicians such as Ben Franklin routinely said things such as "We had daily prayer in this room of the divine power. Our prayers, sir, were heard, and they were answered." Meacham is right that the founding fathers were not sectarian zealots in their own time; what he fails to consider is the likelihood that they would be considered so in ours.
Secondly, Meacham's middle of the road approach fails to grasp how important the extremes of religious zeal were in bringing about major changes in United States history: abolition, the temperance movement, women's rights, and the Civil Rights movement—all major American political movements that were not fueled by moderate mainline attitudes, but by evangelical piety. Real historical change rarely results from moderation. Meacham makes some passing attempt to distinguish the use of the churches for the civil rights cause and the use of churches by conservative Christians to affect political change, but the distinction is spurious. Meacham's religious "extreme" appears to be those who use religion to further causes of which he doesn't personally approve; his religious "moderates" are those who use religion to further causes of which he does happen to approve. At any rate, the fact remains that, in U.S. history, religion has long mingled with politics, and it is not moderate and general religion, but deeply felt and specific religion, that has most often affected true change.
None of this is to suggest that America is a nation where Christians routinely strive to "force" their belief on others. Not even the most fundamentalist of American Christian denominations today advocates anything like a theocracy or the imprisonment of dissenters or the execution of homosexuals or religious tests for office. That is to say, one can be evangelical, zealous, or "extreme" in one's religion and still believe in religious tolerance and liberty; in fact, it is the most evangelical sects of Christians that have historically, traditionally supported the separation of church and state and not the presumably moderate "mainline" Christian denominations, which have tended, rather, to be established state churches.
America may not be a "Christian nation," but it is a nation OF Christians, many of whom are quite zealous compared to Christians in the rest of the western developed world. America boasts a more vibrant, more seriously held Christianity than any other western nation, with evangelicals numbering around 25% of the population. In America, church attendance greatly outstrips attendance in European countries with established churches. What America offers is not "moderation" in religion at all, but liberty, which is what makes real zeal possible. Established religion erodes zeal and slowly kills Christianity. But liberty gives birth to "extreme" religion, life-changing religion, nation-changing religion. What makes America unique is not that we are full of religious moderates or even that our founding fathers were religious moderates, but that most of our religious "extremists," unlike the religious extremists of most other times and cultures, have traditionally recognized that liberty is a friend of true religion.
So, while I appreciate that Meacham does not falsify history to fit it into a mythological Christian-nation mold as do too many fundamentalists, and while I appreciate that he does not wish to eradicate all vestiges of faith from the public sphere as do too many secularists, I am ultimately unconvinced by his thesis of moderation.