Is America A "Christian Nation"?

There is plenty of evidence to support such a claim if one is willing to be selective in choosing their evidences. 

In 1892, for example, Justice David Brewer declared in the U.S. Supreme Court case Holy Trinity v. United States that America is "a Christian nation." Conversely, there is also plenty of evidence against such a claim, including the 1797 U.S. Treaty with Tripoli that said directly, “The government of the United States is not, in any sense, founded on the Christian religion.” So which is it?

While the Holy Trinity decision has rarely been cited by other Courts, Brewer’s “Christian nation” claim was a matter of dicta, not a mandate of the law. “Dicta” is a legal term that means the writing only reflects the judge’s personal opinion, not the legal opinion of the Court itself. Probably the best answer to the question of whether America is a “Christian Nation” came from Brewer himself years later. 

In a book he wrote in 1905, Brewer pointed out the US is "Christian in a cultural sense, but secular in a legal one." The real question, however, is that, given the limitless amount of cruelty, racism, slavery, and genocide upon which the United States was clearly built, why any Christian ever claim America was founded as a Christian nation, since America’s bloody history only undermines the very morality that people like C. S. Lewis and countless others claim Christianity represents.