For better or for worse, I believe this to be true. From the WSJ, 'Under God'

Statistics say America is not only a religious nation but also a Christian one. Up to 85% of Americans identify themselves as Christians. Brian Cronin, who litigated against a cross on public land in Boise, Idaho, complained, "For Buddhists, Jews, Muslims and other non-Christians in Boise, the cross only drives home the point that they are strangers in a strange land." Like Mr. Newdow and the Ninth Circuit judges, Mr. Cronin was on target. America is a predominantly Christian nation with a secular government. Non-Christians may legitimately see themselves as strangers because they or their ancestors moved to this "strange land" founded and peopled by Christians -- even as Christians become strangers by moving to Israel, India, Thailand or Morocco.

As much as some would like to believe that the United States was created under the guise of moral relativism and multiculturalism, the fact remains that it was not. Even if you believe that everyone from the Pilgrims to the founding fathers were extremely welcoming of all religions, it would be hard to make the case that they considered those religions (or atheism) equal to their own. They didn't even hold black people to be truly equal and in many cases they were treated as potential co-religionists.

I do also think that Christian people have the same right to have countries of their own, where their own cultural mores dominate, as do Jews, Hindus, Muslims, etc. This can be done without the establishment of a national religion which is all the constitution prohibits. Believing in God is not a religion, it's a principle.