Paris is not really much of English speaking city. (I travel to Paris often)
A big difference between the larger and smaller EU countries though is unrelated. The smallest countries don't have the budget for dubbing movies and TV series. This really helps with English proficiency in the smaller countries such as the Netherlands.
So while what you're saying is technically true, a lot of shows were only subtitled instead of being dubbed, it is also factually false, that is not the main reason for the proficiency.
I do think the subtitling really helps with proficiency though. School can only teach you so much. Consider Ireland where people get taught the Irish language for 12 years and hardly speak it.
The understanding of different accents, slang, drunken conversation etc can only happen with exposure to native speakers. Content in the original language really helps with that.
Half of English is Latin based, the other half is Germanic based. Dutch is a Germanic language so maybe that's where you're getting the idea from.