America was founded by Christians, but on the principle of religious freedom. The amendments outline what is socially acceptable for us to do in regards to worship, speech, advertising, and even combat. However, while the nation has a guide on how and if you can worship a god, goddess, poster of Van Halen or a rock no one has said we have to worship anything.
This lead to doubt about whether there was anything worth worshipping at all. "Modern Science," fickle thing that it is, demands we prove it first. But how do you prove a negative? It doesn't help that everyone thinks of cathedrals and lighting candles when you say worship - a word which just means to give religious devotion to an object. So you could worship Superman, Master Chief, or Harry Potter if you are a big enough fan.
This brings up the word Atheist itself. Atheism literally means to not believe in any god goddess or higher power that guide you, let alone worship it. This means that not only can no atheist really say "Oh my god!", they don't even believe your worship is valid since your religion is bunk. (And people thought only right-wing Christians were closeminded.)
My point? I don't believe in Atheists or Atheism.