This is just not true. Salty popcorn is very normal in both Europe and Latin America. The artificial butter component is something that is more American and rarer outside of the US.
I can’t speak to Europe, and admittedly my Latin America experience is somewhat limited to Argentina, Chile, and Brazil, and my Asia experience is mostly China, Hong Kong, Korea, and Vietnam. I’m sure there are places where it’s possible to get salty popcorn, but I have found it incredibly frustratingly difficult to find popcorn that is not sweet on my travels. Often if I do find salty popcorn it will be sweet and salty. I certainly don’t like the popcorn I do find, and I get the impression people from those areas wouldn’t like the kind of popcorn that I enjoy. Which I think was the whole point of this subthread, that culinary preferences are often very regional and things we take for granted in one area might be very different elsewhere in ways we don’t expect. I certainly never anticipated what a quest I would have to mount to find something that seemed so pedestrian to me growing up: salt and butter popcorn
