There’s an interesting Gallup poll that compares religious fervor between nations. Here’s a quick summary:
Religiosity is correlated with poverty — the poorer you are, the more godly you are. I guess God really does like that poverty thing.
The US is not the most religious nation, not by a long shot — we are well below the median. It is, however, an outlier, as the most religious wealthy nation.
There is wide regional variation within the US. Mississippi, Alabama, and South Carolina are like poor Middle Eastern or African countries; Vermont, New Hampshire, and Maine are like middle-of-the-road European nations, in terms of their religiosity.
I suspect there has to be a dangerous cycle imbedded in these relationships. Poverty leads to more religiosity as people reach for desperate hope; and religion does nothing to solve real problems, leading to worsening poverty.