A small side note: I believe that there are more differences if one were to painstakingly look into the matter. With globalization, these boundaries are increasingly thinned, so there's no reason to.
The major English locale difference is between the British and American, so regardless of spelling, vocabulary, or even grammar and pronunciation, so long there is consistency of style within a context, it's fine. I don't think it is too difficult for an American to read British English, or vice versa.