1. The Constitution says the United States is a "Christian nation."
The Constitution says no such thing. In fact, it puts all religions on equal footing by banning "religious tests" for public office and guaranteeing religious freedom for all in the First Amendment. Article VI - "The Senators and Representatives before mentioned, and the members of the several State legislatures, and all executive and judicial officers, both the United States and of several states, shall be bound by oath or affirmation, to support the Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States."
2. There are many references to God in the Constitution. There aren't any references to God in that document. The framers didn't leave them out because they were hostile to religion. They simply intended that the government they were creating would be secular. Religion, they believed, would prosper if left in the hands of the people, not the government. Only in the Declaration of Independence is where these references are found, "When in the Course of human Events it become necessary for one People to dissolve the Political Bands which have connected them with another, and it assume among the Powers of the Earth, the separate and equal Station to which the Laws of Nature and of Nature's God entitle them,..." "We hold these Truths to be self-evident, that all Men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty, and the Pursuit of Happiness."
3.Separation of church and state is not in the Constitution, It was invented by Communists, Adolf Hitler, etc. James Madison, considered the "Father of the Constitution," was the primary author of the First Amendment and its separation of church and state. Thomas Jefferson later spoke of that wise amendment as erecting a "wall of separation" between church and state. Church-state separation stretches back to the founders. It's as American as apple pie. "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof:..."
4. The Supreme Court has interpreted the Constitution to say there can be no religion in public schools. The Supreme Court says church-state separation means that kids can't be compelled or requiredto pray or take part in devotional exercises in public schools. Truly voluntary and non-disruptive prayer is legal in public schools as is legitimate study about religion in history, social studies, literature classes, etc.
5. The Constitution does not protect the rights of non-believers. The Constitution's First Amendment protects religious liberty for all, which includes the right not to believe or practice any religion. Americans enjoy more religious freedom that residents of any other nation. Courts have struck the proper balance: Voluntary religious expression is protected, but no one can be forced to support or take part in religion.