Around the founding of the country, the founders had to reject the demands of more than a few religious fruitcakes who demanded the nation be set up according to their personal congregational rituals and babblings. Thank God that they did not allow the establishment of any state religion. They created a nation where people can worship, or not, as they see fit.
78 percent of the population identify themselves as Christian, as is their right to do. No one, including the religious fruitcakes, can deprive them of their right to worship as they see fit, or to identify themselves as they see fit.
Just as for the muslims, when any religion does, or tries to, violate the rights of other citizens, I would join with other reasonable people to declare them not a religion, but a political tyrannical group that is not compatible with the US Constitution, not protected by our First Amendment, and not compatible with any human civilization.
Thomas Jefferson did argue effectively for not having a state religion, but that was only for his state. South Carolina went its own way (among others).
But I'm not advocating for religion sponsored by the states (not federal); I am advocating for the free expression (which that has been cut off now). Also, if a state wanted to adopt an official religion, they are free to do so: the issue is, application; and that would be tricky.
And as for Islam, it cannot exist alongside Western Civilization without it eventually violently clashing with it when the numbers are appropriate to do so (see Europe), and read "Secrets of the Koran" by Don Richardson. Allen West has spoken most clearly on this. President Adams also knew this to be fact.
And I don't give a rip if 78% call themselves firetrucks. That doesn't make it so. Jesus set the standard: "Ye shall know them by their fruit". We don't even act like a Christian nation. That was my point.