I was once chatting with a co-worker about why English is so prevalent in the Netherlands and, particularly, why Dutch people tend to speak English with American accents.
My co-workers theory: it's because American English was heavily influenced by Dutch speakers in colonial times. e.g. New York was once New Amsterdam
My theory: in the Netherlands (at least in the 1990s), American TV shows were not dubbed but had subtitles instead. This allowed teenagers who watched American shows to learn English but with an American accent.
Open to other thoughts and suggestions.