Kek I like how that fits.
No, actually, you're wrong there. We're taught UK English (I remember getting a 9 instead of 10 because I used pants instead of trousers iirc).
I learned "American English" from movies, music and the biggest influence, video games.
I stopped "learning" (in the true sense of the word, as in, actually exercising) English uh.... 5 years ago ? I think. Or maybe 6... that's not the point... I've only practiced English over the last whatever years from typing it on forums/games/chat and listening/reading it on movies/music/games. I don't speak it daily, as I do my mother tongue, so I am bound to sometimes make mistakes.

