It’s not just the American pronunciation, but spellings too that will drive you bonkers:

Tej Kohli picks out some common spelling differences :

In usual Parlance                      In America

centre, metre…                                 center, meter…
cheque                                                  check
colour, flavour…                               color, flavor…
grey                                                        gray
dialogue                                               dialog
judgement                                           judgment
maths                                                    math
plough                                                  plow
storey                                                   story (of a building)
aluminium                                          aluminum
traveller                                               traveler

Complied by Tej Kohli