Actually no. The non-homogeneous states in America with lots of Nordic peoples tend to be the best governed as well. Think Minnesota ("think Minnesota" is the answer to every statistic comparing Europe to the States, crime, gun control, healthcare, etc., because Minnesota is basically Yankee Switzerland on every statistic). Almost as if it's not about the legal structure, but rather the people.
It's more like if you rated everyone on the planet on "does this person make the place where he lives a better place or not", Scandinavians (and their descendants) would score perfect 10s.
A geneticist friend of mine has an explanation for this: he thinks that adaption to civilization makes us more nepotistic. He contrasts guest-rights in Northern Europe with "my brother against my cousin, my cousin against the stranger," of Egypt. When he gets melancholy, he will tell you that future of civilization is Mesopotamia -- where we have been civilized the longest. And Idiocracy.