Atheism is the lack of belief in God/s. There’s no cause, no worship, no book, no claims, no prophets, no messiah, no sins, no afterlife, no praying, no demons, no deities and no faith or belief. So by default, not a religion. Try tackling a subject you know something about.
By the way: In many ways, Atheism, as practiced by the Sam Harris cultists and Penn & Teller acolytes, is a religion. As with Buddha, atheism has all the dogma of any religion without a deity at its center.
So, to be honest, most everyone in America is religious in some way.