This big religious-identification study is getting a lot of attention, and justly so, for showing the rise of freelance religiosity on the one hand, and straightforward secularism on the other. (The two trends blur into one another, obviously.) If I may take the liberty of dipping into my own archives, I think this piece from 2007 on a similar theme - I focused on the parallel rise of European-style secularism in the U.S. and American-style culture war skirmishes in Europe - holds up relatively well. This point, in particular, seems worth highlighting, amid all the bright talk about how Barack Obama's going to end the post-Sixties kulturkampf:
Religion stirs up the most controversy, a group of Harvard economists recently argued, when roughly half the population is actively religious; conflict ebbs when the devout constitute large majorities or small minorities. The more evenly divided a culture finds itself on the ultimate questions, the more likely politicians are to pursue "strategic extremism" and mobilize one side against the other. Precisely this kind of polarization dominated European politics from the French Revolution until the middle of the 20th century, sparking regular clashes-- Germany's Kulturkampf, France's Dreyfuss Affair, Spain's Civil War--between secular and religious ideologies.
America has long avoided this trap by enjoying near-universal piety; Europe, at least lately, has escaped it by cultivating near-universal skepticism. But if the religious gulf between the two continents narrows, the divides within each one are likely to open ever wider ...
In other words, unless conservative religiosity goes into a steeper decline than is visible in the latest data - and such a decline is possible, of course - the growth of "Godless America" may only make the culture wars hotter over the short run.