"Make workers (relatively) really rich by the world standard, and they will be probably less religious, but that works only for native-born workers of the North, and that doesn't seem to motivate them to socialism or communism."
Me:
Maybe. According to the Cambridge Companion to Atheism (2005), though, quite a number of the world's poorer countries are very atheist -- Vietnam beats the US, France, Norway, and others. Even Armenia beat the USA. In a Top 50 list, number 1 being most religious, 50 being least, America was number 44, and more atheist than it were countries like Uruguay, North Korea, Kazakhstan, Mongolia, Czech Republic, etc. Ironically, Cuba was no. 49, barely in the Top 50:
http://www.pitzer.edu/academics/faculty/zuckerman/atheism.html
(Methodology of survey is there.)
-B.