On biscuits and bubble and squeak we have had discussion before - try a search.
I read that Rowling was told that American children would not understand the reference to the Philosopher's Stone - not many of my 8 yr old addicts would have done, either.
Can anyone tell me why Diana Wynne Jones' books, by a British author, set in Britain, often have not only US spelling but vocabulary - sidewalk, fender, tire, trunk etc, in British editions, while American authors such as Judy Blume and Betsy Byars are available in UK English? One even had the internationally accepted spelling aluminium, which is not used in science journals. We have to write sulfur and do, but aluminum still gets used the other way round.