Great thought provocating and humorous story.
I'm from New Zealand and I can be very open to strangers on the street, last Christmas I invited a van load of travellers to my house for Christmas dinner in Adelaide because they were looking at spending it in 40-degree heats out of the back of a van.
However, when I head into more foreign environments (outside of the Oceania) I seem to put up a weary resistance to those around me. I'm not a fan of the reaction but it comes so disturbingly naturally.