I live in the Netherlands, I can explain why so many Dutch people speak English here fluently.
We have a lot of television, games and other multimedia here not being translated to Dutch.
TV gets subtitled, but audio remains English.
This way children get adapted to the language early on, even though more cartoons and games get dubbed these days.
But even then, Dutch Wikipedia pages usually contain little information compared to their English counterparts, a lot of stuff found on Google is unavailable in Dutch (especially tech-related things), those are factors that make English a crucial part of the lifes of older people too.

Looking at our huge neighbour: Germany.
Everything must be translated or dubbed to German before anyone gets their hands on anything.
As a result, a lot of Germans can only speak German, even though the English lessons at school are equal to the English lessons here.

I don't know about Scandinavia and Iceland, but I expect them to have similar reasons to the Dutch.

People from Scandanavia (Sweden, Denmark and Norway) and the Netherlands are renowned for speaking excellent English.

My parents live in Amsterdam and they don't speak a word of Dutch. They said that in the entire time they've been living in the Netherlands (three years now), they've only met one person who couldn't speak English. I can confirm from my time over there that just about everyone speaks English as if it were their second native language. When I was in the Dutch countryside I met people whose English wasn't as good, but it was still what I'd consider 'fluent'. 

I haven't spent much time in Scandanavia: I visited Copenhagen for a few days. Based on my brief time there, everyone spoke English as well as people in the Netherlands.

I've found that people in the other Germanic countries (Austria, Germany and Switzerland) generally also speak English fluently, but they <em>generally</em> had slightly stronger accents than the people in the Netherlands and Scandanavia.

True, Scandinavia rocks a great english accent. Iceland have a great accent too.

Europa

Only one person I met in Sweden couldn't speak English. He was probably in his late sixties. An old gentleman brushing up leaves and shoveling them into his wheelbarrow to clear the driveway. This was two years ago in November. I wanted to know if he needed help so I just wandered over and asked. He didn'tunderstand a single word. I was gobsmacked! Everyone, on all my trips to Sweden, had understood me (despite occasional shynesses when speaking). So I mimicked me helping him by shoveling what he brushed. He seemed okay with the idea as I pried the shovel out of his hands. 

Funny thing happened a year later. I told an interviewer that story and it got me the job.