There is an interesting line of thought that high trust societies are caused by out-breeding. The medieval european church forbade cousin marriage for centuries out to something like third cousin. This broke up the clans and arguably made cohesive western nations possible. Today in much of the non-western world first cousin marriage is still normal. I believe most arab marriages are to first cousins. In the places where it's most prevalent you do tend to see clannish behavior and indifference/viciousness to the out-group.
Dunno if it's really true, but it does seem to fit various historical developments.
With China I think maybe you have to keep in mind what a scarring catastrophe Maoism was. Middle class people and values were systematically purged.