Atheism - People actually believe this

The US as a nation is a product of a lot of non-religious forces. The current turn towards being a "Christian Nation" is a product of the cold war where religion was used as a differentiation between the 1st and 2nd worlds.

I don't know what's worse about this

You have the obvious slippery slope idiocy.
They also don't seem to be aware of the role of the enlightenment in the founding of America

Also there's one of the religion's most obscure figures whose teachings they're going against. You see this "Jesus" guy was okay with secular governments and wouldn't like bearing false witness against your atheist neighbors.