> It sounds as though people in some countries interpret it as if the smiling person is on the inside of a joke and you're on the outside, or even the object of ridicule.

I would say this is pretty common in the USA. Anyone smiling or laughing, especially in the customer service industry, can easily be interpreted that they are up to something. Makes customers uncomfortable. Obviously a generalized statement, but it seems most food and customer service industries despise their customers.