A really interesting topic (leading me to figuring out my long-lost password to actually participate!).
What I don't agree with at all is calling "American English" wrong. It's just a different dialect or variety of English with it's own spelling. Nothing wrong about that.
I find it hard to say which "English" is more important or popular around the world. Me being from Germany, I learned the British English in school which I guess is what most people learn around here.
Still I feel that American English (or American accents) is on the rise as the (english speaking) media (in Germany) is heavily influenced by the U.S. (I would put my guess at more than 80% of music/films/television etc.). Although Britian naturally is basically just around the corner, the U.S. is more important economically which is influencing the English accent CEOs and business people are picking up and so forth...
Then again a lot of students go studying abroad in the UK while just as many prefer going to the US, Australia or Canada picking up the respective dialects.
For a non-german speaker I could honestly not tell a big difference between Canadian and American accents by the way while travelling through the north-eastern part of North America (New York, Chicago, Toronto, Winnipeg). I sure can tell the difference between British English and American English though...
And as far as my spelling goes, I am generally switching back between Britsh, American and Misspelling 
Teachers told me just to stick to one version in school but they sure didn't tell me spelling "colour" as "color" is a mistake.
So all in all I would say that it's not really a black or white topic...
