"Modern day Japan is for all practical purposes an Atheist country yet their society seems to be doing fine. "
You should do some more research on this. I would not say they are doing fine for several reasons, one of which is that they have an extremely high rate of suicide (it's not discussed very openly). In fact the gov't has become concerned about online "suicide pacts", which they are afraid will cause even more people marginally predisposed to commit suicide to actually go through with it.
BTW, ever been to Japan? Your point about them being an atheist country shows your total ignorance about Japan. They are a very spiritual people and would never call themselves atheist.
What role does religion play in Japanese society? Almost none.