Very interesting.
My guess would be, that it also depends on what languages people are tought in school. There are countries where English is mandatory. Reddit tells me, while English is kinda wide spread in Russia, it is not everywhere so. They teach anything from German to Chinese as a secondary language.
While you might not be able to hold a conversation with your school English, it might be enough for most games. But it might be a different scenario entirely if the game is very story and dialogue heavy.