As an American working in the UK, I was surprised to discover how often Brits and other Europeans assumed that genuine friendliness was "fake friendliness". Their own attitudes toward others were assumed to be universal, so any sign of friendliness that they wouldn't have expected in their own society was assumed to be fake.

Yes, sometimes it is fake, but very often it's a case of being unable to imagine a culture where genuine friendliness toward strangers is a lot more common than what they themselves tend to feel toward strangers.