I have this general feeling based my 21 years bouncing around Europe that subtitle countries have better English than dub countries, although I'm not proposing that the link is causative
It's definitely a contributing factor. Living in the Netherlands, Dutch kids learn English through Youtube and Tiktok. Since it's a small country there's less Dutch spoken online, as opposed to German which has dubs for a lot of movies / TV shows.
My perception from traveling to 40+ countries is that countries where dubbing is common do so for the reason that the population is more illiterate and lower-educated in general, and that trend just extends to having less fluency in other languages.
There are many reasons for the distinction, culture and money being chief among them.
Dubbing is far more expensive than subs. So countries like Germany or France would be more likely to afford it. They're also countries which try to promote the use of their language for historical and national pride reasons (as opposed to Anglicization of everything) so it makes them even more likely to have dubs. They also had dubbing for so long that it became cultural and maybe even expected.
Contrast that with countries like the former Eastern block which had no foreign material to speak of until the '90s, and when they finally did they couldn't afford dubbing, so they went with the quick and easy route of subs. They also probably have fewer aspirations for the promotion of their own language and priorities practicality over pride, embracing foreign languages faster.
I don't think that is true. France is a highly educated country, while for them dubbing is a part of culture. I would say the same applies to Japan and China. I'm neither one of these nationalities.
It's just smaller vs. larger languages making dubbing more worth the cost. Education in France and Germany isn't worse than elsewhere in Europe. People there do speak English slightly worse and with a stronger accent on average.
