Spend enough time on Facebook and you could be forgiven for thinking America is engaged in a contest between Christianity and Islam, with every state apparently defined by its religious loyalties.

There’s an interesting omission in many of these conversations.

According to the Pew Research Center, 29% of American adults have no religious affiliation. That’s considerably more than the 19% who identify as Catholic, and nearly 30 times the proportion who identify as Muslim.

These Americans include atheists, agnostics and people who describe their religion as ‘nothing in particular’. Some believe in God. Some consider themselves spiritual. Others have no religious beliefs at all.

Meanwhile, Muslims account for around 1% of American adults.

Religion undoubtedly influences American politics and public life. Yet the attention given to particular religious groups can leave us with a distorted impression of who Americans actually are.

There’s a difference between the size of a religious community, its political influence and the fears people attach to it.

And perhaps the most interesting story is the one receiving considerably less attention.

Almost three in ten American adults have stepped outside organised religious affiliation.

What does that tell us about the America we think we know?