I read several comments in support of smiling as a universal form of politeness, which in itself is a sweeping generalisation that doesn't acknowledge cultural

I read several comments in support of smiling as a universal form of politeness, which in itself is a sweeping generalisation that doesn't acknowledge cultural differences. BTW, I'm not pissing on Americans, in my experience Americans are generally considerably more polite, friendly and open than most other Westerners. But the way that is expressed is not a universal language, which tends to lead to misunderstandings.