Here's Richard Dawkins take on religion in Europe (in a recent weekend interview in FT): 
While he explains thus the idea that constitutional separation of church and state has helped American religion:
"In the US, religion has become free enterprise, with all the benefits of high-pressure advertising and marketing."
I remember while I was interviewing last April for a planning job with a research consultancy here in Singapore, they asked me why religion is so intertwined with politics in the US while it kind of lays dormant in Western Europe. I wish I had this explanation by Dawkins then.