It's coming from all over. It always has. It was understandably never so visible for people who don't hang out in casual international spaces, but it's not new and it's not owned by anyone. The reason it's so compelling isn't actually the lack of AC, it's because it's an easy button to push that gets people living in certain countries very defensive over something rather trivial.

I mean the lack of AC is definitely weird for a developed country, and the deflections about mild climate certainly aren't a posteriori, but it's the defensiveness and cope that makes it a button worth pushing in the first place.