> One might also argue that the history of belief in personal sin makes European cultures more self-depreciating, but I feel the Japanese are more self-depreciating than the Europeans.

I think that has more to do with collectivism vs individualism, which itself may be to do with hierarchy and community. Those values may have been endowed through religion over time, but I don't know enough about Shintoism or Buddhism to comment on if it influenced Japan into becoming a collective focused society.