Interesting, why Scandinavians are better in English? Those Nordic countries are relatively small.. Maybe some countries have large internal communities so theres no incentive to attend to international sites. I wonder if its the case for China.
Warning : long post.
Well first of all the divide is partly based on European languages. Norwegian, Swedish, Danish, Dutch, German : those are all germanic languages, like English. French, Spanish, Portuguese and Italian on the other hand, are all Latin languages, which means they are much farther away from English (French being closer than the others for various reasons). This means it's easier for them to learn English.
An other factor is necessity : speaking Swedish isn't going to get you far outside of Sweden and Finland. If you speak Spanish OTOH, you've got all of Latin America (minus Brazil) speaking your language, more or less. If you're French, that's half of Africa right there. So there's less necessity/incentive. France, Spain and Italy are also much bigger countries (in terms of population) than Sweden or the Netherlands, which means it's a lot easier to just stay in your country where people speak your language. This is somewhat what you're saying with the community sites existing in our own country : for example in boardgaming, there is this huge international site called BGG, but there aren't a lot of French people there because the second biggest boardgaming site in the world in French (Tric Trac), so most people don't really feel the need to go to BGG. None of this really applies to Germany however, and I do believe Germans aren't as good at English as Swedish or Dutch people (although I'm basing this on no actual numbers so it could be completely off).
And then there's the school system. Scandinavian countries, Sweden in particular, are notorious in Europe for being better at everything than everybody else (I'm not saying it's entirely true, I'm saying that the perception). The French moderate left has been dreaming after the Swedish model for years now. Meanwhile, the French school system is completly and utterly broken, especially when it comes to languages. The way we learn languages is mostly through reading and writing, which is all well and good in theory but in practice speaking and hearing a language is much more important, but the French school system in general punishes taking risks, which you are doing if you're speaking a foreign language in front of the class : you will make mistakes and the teacher will correct you, sometimes even interrupting you. This might seem like a small thing, but it's actually an important part of why we suck at foreign languages in general : participation in class is not valued by the French school system, and it is an essential part of learning a language. I can't speak for other Latin countries in that regard though.
One other thing are movies. I believe most movies shown in Scandinavian coutries (and possibly the Netherlands ?) have the possibility of being watched with subtitles instead of dubbing. This is not true in Latin countries. Simple example : I live in a medium-sized French city (Le Havre, 12th biggest city in the country), and I haven't seen Guardians of the Galaxy yet because I would have to go to Paris to see a subtitled version instead of a dubbed one. I believe Germany isn't much better than us on that front though.
I will note that this is changing. For example in the French school system, you used to start learning a second language in sixth grade, where you had the choice between German and English. Until the 90's or so, German was often favored by good students because it had the reputation of being harder and thus going in the German class meant you were in a generally better class, so parents who knew this would push their children to take German. This is simply not true anymore, as everyone by now realizes how necessary it is to speak English, so German as a second language is simply disappearing and will probably no longer be an option in a few years if you ask me. I think English is also starting to be taught at an earlier age these days.
Oh and there's an other factor : culturally, Northern, protestant Europe, is simply closer to the UK and the US than southern, catholic Europe. Germany is again kind of in the middle there, but the point still stands for the most part.