I would love to find a reason to say that atheism is a contributing factor in a well balanced and civilized society but I just don't think it is. Sweden is often cited as non-religious but in England most people are considered religious by default because of the state sponsored religion. When the census takes place most people just assume they are supposed to write Church of England but they won't have considered it, religion is largely a non-issue here.

I think there are far many other more likely factors. America is significantly more right wing than most of Europe and I also think there is a greater sense of entitlement than in much of Europe.

My feeling is that overall religion is a negative force. In my experience that is a popular view in England although as I say I think they majority simple consider it irrelevant.

To directly address the question, in general I don't see how atheism can be considered a contributing factor in anything as it is simply an absence of one belief, not a statement about the presence of another. However, if the societal norm is to be generous then religion will amplify that and may place a greater obligation on members of society to continue the practice.