Godlessness is also a "religion." You do understand that, don't you?
Sure. The same way "bald" is a hair color.
No, seriously. The belief that there is no God is constitutionally protected in First Amendment. The clause "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof" means that the government cannot force atheists to recant and adopt the opposite belief.
In other words, if atheism were not a "religion", your right to be an atheist would not be protected by the United States Constitution.
Is that what you really want? Choose wisely now.