The belief in Shintoism and Buddhism and all the fact that all Japanese are related help the Japanese live in an over crowded society.
Culture norms and values are greatly influenced by beliefs . The actions and behavior of people are based on beliefs and cultural norms.
Shintoism is basically ancestor worship ( animism is belief that the world is inhabited by spirits, spirits in the water, trees, and most importantly spirits of people who have "gone' before". ) In Shintoism respect for the ancestors is a very high value. Since all of the Japanese are related to disrespect another Japanese is to disrespect the ancestors. The beliefs and values affect how the Japanese treat each other.
As belief in Shintoism fades it is predictable that the values based on Shintoism will also fade. As these values which are based primarily on tradition instead of belief fade respectful behavior will also be lessened.
Buddhism has disciplines of meditation. The Japanese gardens are set up to create calm and mental relaxation. The tea ceremony is another Buddhist tradition designed to create harmony. The disciplines of Zen Buddhism are practiced by many people in Japan that do not presently believe in Buddhism.
The sense of community created by all the Japanese being the same ethnic group promotes hard work, willingness to obey the law and respect for other people in the community.
How to transfer these behaviors to other societies that are not as ethnically uniform as the Japanese is hard to answer. Also how to promote belief systems and values that create community is a difficult question.