Any small town will be friendly. Generally, the less tourists they get, the friendlier they are.

New York is not a friendly place because there are so many tourists (and immigrants) there that people are sick of it. They don't have any desire to meet anyone new. Some random small town in the middle of nowhere is likely to be friendlier because they don't get many visitors, so when they do, they are curious and want to learn more.

Controlling for city size, I have found the friendliest people to be rural Britain, New Zealand and perhaps some parts of the US South. The friendliest big city would probably be Sydney. I have heard that Iran is very friendly if you are brave enough to go there, but I haven't.