In terms of language, there will be some English speakers in every faction, but they vastly speak the language of that faction. I know that the Dutch have quite a few english-speaking or bilingual members, I can't speak for France, Denmark, or Spain because I don't really talk to them so much as shout obsceneties over broadsides.
Honest advice- just pick the nation you like the most, and think you'll have the most fun with. If it doesn't work out, you can always switch.