Rachel Shukert, who is Jewish, nominates Thanksgiving to replace Christmas as America's biggest holiday:

Religious holidays have their place, and that’s in the homes of the adherents of that religion. It’s when a religious holiday aims for a universality, that, by definition it cannot have, that we have a problem. No matter how much we spin Christmas as a "winter festival" with pagan origins, the first six letters of its name are impossible to shake, a proverbial nail through the palm.

Why Thanksgiving is better:

It’s a nice long weekend and usually not too cold, there are no religious services of any kind required, and you get to start drinking and eating at 3:00 in the afternoon, which is always the time that everyone is hungriest anyway. Its message of thanks is easy to get behind. "We can’t have a tree because we don’t believe in Jesus," my mother used to say to me, but it’s pretty hard to argue with being grateful that Grandma’s cataract surgery went so well or that they finally made a movie of Les Misérables.