It's all about comfort levels. Comfort is based entirely on what you are used to. When you find yourself outside of your comfort zone there is at best discomfort at worst fear. It's part of the fight or flight mechanism when we deal with new or different circumstances.
For example: When I lived in Poco for 5 months I became used to being surrounded by multicultures. Chinese, Vientnamese, Phillipeans, Mexican, Canadian , you could walk down the street and pass a different nationality with each step in some parts of the city. So it became normal. I learned to say hello in multiple languages and smiled at everyone. However... it has been a few years. I can't garentee that I would still know what to do if I found myself in the same situation again, not for a few days anyway. I also had a friend who was completely overwelmed by it (also not from there) and would become utterly speachless because she just had no idea what to do and it intimidated her.