Since we had a post about the most friendliest countries, we should look at countries that have unexpected friendly people, not the usual answers like Ireland, Scotland, Canada, Taiwan, etc. For me it’s Montenegro. Londoners are considered to be cold and rude but I find them to be very pleasant with me.
Iran has been by far the most friendly and welcoming people. And I visited -a lot- of places.
Also USA had very welcoming people, I must have been lucky by judging from people online, but in real world, my experience has always been very positive.