Scamandrius, doesn't your assertion assume then that people used to go to church as a form of "welfare"? That they were wooed to church in the hopes of handouts?
That doesn't really speak very well about Christianity, does it?
I think that a link between the rise of welfare and states becoming more secular is hard to prove.
Rather, I tend to agree with Robert Putnam, whose book, "Bowling Alone" points out that as our society becomes more individualistic and less family-oriented, then people have fewer support systems - of any type. (http://www.bowlingalone.com/
). Putnam argues that Americans are less civic-minded these days - they join organizations like PTA less, and that goes for churches as well. (The book's title comes from the fact that more Americans are bowling alone, and fewer join leagues).
Putnam also points out that for families who have to commute a long ways to work, their chances of joining civic organizations is even less, because these families spend so much time driving to and fro in their cars.
So I think socioeconomics might affect people's church attendance. But what's welfare got to do with it? Welfare has been rolled back, starting in the '90s, by then-president Bill Clinton. And yet younger generations (Gen Y or Millenials) seem less likely to join churches than older generations.