The spell check itself was a problem because even Americans and Canadians, who speak almost the same language, spell some things very differently. Americans and the British, whose languages aren't even remotely similar, also have huge differences in the way they spell or pronounce words. "Schedule," for example is spelled the same way in both the U.S. and U.K, but is pronounced "sk-ed-yoool" in the United States and "schrrrruruuuullllll" in England. No one is certain what the British intend to communicate using that sound, but they put great importance by it, so it's almost certain to be offensive.