A study of 32 countries shows that the most diverse populations also smile the most. That makes the USA among the smiling-est places in the world
Apparently, smiling is part of the non-verbal communication that proves to be helpful in building trust within diverse societies.
There’s also a difference in why people smile. In more homogeneous populations, a smile might not represent friendliness…it might instead be a way of appearing superior or higher up in the society’s power structure.
So, for example, when WalMart expanded to Germany, the company stopped requiring sales clerks to smile at customers – a habit German customers had misinterpreted. And when McDonalds opened in Russia and wanted to appear American, the company had to teach workers to make eye contact with customers…and smile.
Finally, from an article in The Atlantic – this post from a Reddit user in Finland:
When a stranger on the street smiles at you:
a. you assume he is drunk
b. he is insane
c. he’s an American