To paraphrase P.J. O'Rourke, this country was established and settled by gun-totin' Christian zealots.
On the other hand, in matters of government, the most notable atheist and pagan contributions inlcude the Soviet Union, Communist China, Pol Pot's Cambodia, Castro's Cuba, and Hitler's Germany.
You live and breathe free because of the efforts and sacrifices of gun-totin' Christian zealots. If you had been born in an atheist/pagan paradise at any time in the last century, you would have known gross deprivation, misery, and quite possibly an early liquidation courtesy of the great atheist/pagan state "newer and better proletarian/volk" extermination machine.
I only wish the ACLU and their siamese twin libertarian brethren would settle an isolated island together somewhere. Within a generation it would be "Return to Pitcairn Island" complete with mass murder and cannibalism.
On the bright side, none of the citizenry would have to suffer the intolerable and insufferable placement of granite monuments to the Ten Commandments in their courthouses and extermination camps.
If not for the "establishment clause" in the First Amendment, some (but certainly not all) of the Christian zealots you have referred to would use their religious beliefs as a benchmark for political office and employment in the public sector, and reduce those who don't believe and practice their particular religious persuasion to third class citizenry.