America is not a Christian Nation
One might argue that America is a Christian country simply because a plurality of its citizens self-identify as Christians. The religious right is either making a much more substantial claim or committing a logical fallacy.
Theocrats often use the "Christian country" claim as a key premise in arguments of the following form:
(p1) The United States of America is a Christian country.
(p2) Christianity abhors usury.
(p3) Christian countries must not permit anything abhorrent to Christianity.
(C ) Therefore, the USA must not permit usury.
Suppose (p1) means “Christians comprise at least a plurality of American citizens.” On this weak reading, the argument derails, even if we grant (p2) and (p3). So what if a majority of Americans are Christians? What matters is whether a majority of Americans vote to ban usury and whether the proposed anti-usury legislation is constitutional. The weak version of (p1) doesn’t do any work. If that’s all the “Christian nation” claim amounts to, the argument reduces to a civics lesson.
Consider a stronger reading of (p1): “The constitution of the United States of America requires that laws conform to Christian doctrine.” Alternatively, “The constitution forbids any laws that violate Christian doctrine”; or “The constitution requires that we pass all and only those required by Christian doctrine.”
The sample argument makes a certain amount of sense on the strong reading of (p1). The strong reading has a significant drawback, however—namely, that (p1) comes out false. The constitution just doesn’t say anything like that.
Well argued like the philosopher she is. But there is a more direct argument. On June 10, 1797 John Adams signed the "Treaty of peace and friendship between the United States of America and the Bey and Subjects of Tripoli, of Barbary," a treaty negotiated by George Washington and ratified by congress. This treaty had a line that was not considered radical or controversial at the time, but is quite interesting today:
...As the Government of the United States of America is not, in any sense, founded on the Christian religion...
At the time this passage was required because Barbary would not deal with Christian nations so our Founding Fathers had to put this core difference* between the United States and the European nations in writing.
This nation inherited its Christian thoughts, laws and traditions, but it was not founded on Christianity. America was founded on what was at the time a competing philosophy, The Enlightenment. Unfortunately, I believe these two philosophies are competing yet again. Let's hope the reigning champ maintains her title.
* Yes, I know Democracy was also a core difference. I said "this" core not "the" core. Sheesh, the little voices in my head sure like to argue.