PS as an atheist, you know how to tell the difference between an atheist and a militant Atheist? One of them capitalizes it.
My definition is that they, like their polar opposites, are the ones always screaming about it. The US is 74-85% Christian, but that runs the gamut of "what's on their birth certificate" to loud-mouthed Bible thumpers. About a third of those are Evangelicals. Atheists are a much smaller number, about 2-4% although Atheist groups like to fluff up their numbers by including Buddhists, agnostics and anyone who says "no religion".
Poll: Most Americans Say They're Christian