That's strange, the United States certainly seems to have been chugging along just fine the last 300 years, even though we've never been a homogeneous populace. 

At the same time, Japan, a nation that IS very homogeneous, is the poster boy for unhappiness, having one of the highest suicide rates of the developed world. [In fact, it just peaked at an all-time high. 
](https://www.nytimes.com/2018/11/06/world/asia/japan-suicide-children.html) 


Visitor from a parallel Earth? Or just plain wrong? You decide, dear reader!