Often in fiction, whenever the President of the United States enters the scene as a bit player, it’s a black man or a woman just to emphasize how different the fictional world is from the current one. This is especially prevalent when the work is set 20 minutes into the future like a disaster movie.
However, polls have that atheists are the most unelectable minority in the US. Has there been any work of fiction that casts an explicitly atheist president? I can’t think of any off the top of my head.
Kevin Pollak played a President who explains that he’s an atheist in DETERRENCE, though it’s hard to tell whether he’s making a serious point or just being kind of a dick.
The Ides of March featured an atheist George Clooney running for president (in fact, the movie opened with him at the podium during a speech or debate or something admitting it). My wife and I both fell asleep in the theater, so we have no idea if he was ever elected or not.
There’s been any number of actual Presidents whose religiosity was probably a front. You’ll find plenty of people in any church who don’t actually buy the stuff they’re selling, but they attend anyway for the social benefits.