Lots of Europe especially France is packed with smokers. One of those things you take for granted living in the US and once you travel abroad you realize how much of the world still burns tobacco and it’s everywhere.
I'm not American though and while smokers are everywhere here, I don't recall ever being on a flight where smoking was allowed, even though the one mentioned was a connecting flight through Paris.
They've mostly switched to vapes now. It's still annoying, but at least it doesn't leave trash all over the streets.
Seeing the sidewalks / parks outside of the main train station in Prague covered in cigarette butts as an American tourist in 2019 was certainly something.
Italy too. It's bizarre trying to hop on the trenitalia trains while a bunch of random people are standing on the platform right in front of the doors trying to get a few last drags in before the train leaves.