Re the difference between Canada and the U.S.: This is anecdotal, not proof of anything, but for what it's worth:

I grew up in very rural Minnesota, on a farm with little villages a few mile in each direction. In 1975-76 I spent a year a few miles above the Minnesota-Ontario border, pastoring a small rural church as internship for seminary. The church members promptly noted to me that there was a much lower percentage of church attendance in Canada, which I soon found to be true; I was a little surprised, as about the only other cultural differences I could see were "ayes", mild accents, and a craze for hockey instead of football. A few folk were staunch church people, just like a much higher percent back home. As I dropped in on other area residents, they were open and cordial, but just not interested in church attendance. I don't remember any of them professing atheism, but I don't think I ever asked directly.