Research Report: How Secular Humanists (and Everyone Else) Subsidize Religion in the United States
One of the more interesting speculations here is that one reason the USA is so much more religious than the rest of the Western world is that a large percentage of churches in the US would not be able to afford to operate if they were not directly or indirectly subsidized by everyone else. The numbers here are surprising.
For those interested, this issue has some excellent articles on debunking the current claims that the USA was founded as a Christian nation, constitution and all, as well as the historical debates about that; many which sound very familiar today.