My correlation of data on human development index vs religiosity in the USA might be explained differently than by the security hypothesis. For example, founding populations were in many cases religious refugees seeking to escape persecution from governments with established religions.
Still, the security hypothesis to explain the correlation seemed pretty persuasive to me. I took a quick look and came up with a confirmatory piece by Nigel Barber here. A salient quotation from the article:
“The bottom line, then, is that Americans feel far less secure economically, and in relation to their health and well-being, than would be expected given the overall wealth of the country in terms of GDP per capita. This existential insecurity provides a fertile ground for religion. Scholars might appeal to historical factors such as the Puritan founders but history counts for little in these matters given that virtually every country has a devout past. “
Barber mentions, and I think it important, that Americans interpreted the tremendous success of their economic development as a reward for their faith in God. They tend to dismiss the fact that their possession of superior weapons and a willingness to use them on the inhabitants of the territory allowed them the opportunity to freely exploit the natural resources of a huge part of North America. This is the real basis of American power. But current events dictate current views. Things are not going well in America, and this has been true for some time now.