While I was working at an English summer school for teenagers this year, I noticed that the bottom class was always made up of French, Spanish and Italians. The Eastern European, Swiss, German, and of course Scandinavian and Dutch students were way ahead.
Why? It has nothing to do with the French brain (as I have been told on more than one occasion) or the French language being so complex that if you speak French, then your brain has no room for any other languages. No. That's just a terrible excuse.
A big reason: in those countries where every person seems to speak fluent English, their TV is subtitled not dubbed. This makes a huge difference. I've had amazing students at the school where I used to teach (hello ECE students!) who speak English that is so good, I thought they must have lived in America. But no, they were students who watched all their favourite TV shows in English. If you have children, you may not want them to watch more TV. Yet the best thing you can do for their English is get them to watch TV in English.
If you want to speak a foreign language, you need confidence to just go and speak, when you know you will make a lot of mistakes. Putting yourself out there for possible humiliation is scary. And, in my opinion, English teaching in French schools does not often help students' confidence at all as there is too much focus on what students are doing wrong, rather than what they are doing right.
I could continue, but I will let the experts who spoke to the Local newspaper tell you some more. And if it's any consolation, the English are pretty bad too.