The United States is an outlier when it comes to religiosity.
Typically, the most religious nations are also the poorest. This graph shows that the US is more religious than Eastern Europe and not far off some middle-eastern states.
This shows that something very different is happening to the US. Typically, wealthy Western nations are becoming increasingly less religious.
The best explanation seems to be related to equality. The US, although wealthy, has low income equality. Equality seems to be a very significant predictor of all sorts of other social indicators, including crime, prison population, and longevity.
If we plot inequality against religiosity, then suddenly the US is not an outlier. It's right on the main sequence, somewhere between India and Bangladesh.More questions on religion: