Id say the difference isnt the language its the use of it, I went to Uni in England (before tuition fees !!) and they are not so different in the use of the language, some words are different and the prounounciation is different, but the difference between british English and American is sarcasm, all the Americans I have met dont seem to get sarcasm , which is used alot this side of the pond. Its been describes as the lowest form of wit, but its got its place.