Forgive me if its been asked, but somehow I doubt it.
The northern nations, Canada, Norway, Sweden, Finland, et al, are significantly less observant in religious practice than more southerly countries, such as Italy, Spain, Mexico and the USA. This seems to be the case as well with countries in Asia, though China has legal restrictions.
In fact, in many cases, actual belief in gods is lower as you go north. None of this is much in dispute: the CIA world factbook, wikipedia and national census’ report these facts well.
I know the question I ask is obvious: Why? How would you do a survey, census or research to find out why? Is it even possible?