Given the amount of places around the world that English is spoken, various differences are bound to emerge. American English often differs in intonation, word stress and vocabulary, and, to a much lesser extent, grammar and sentence structure.
The first large American dictionary, An American Dictionary of the English Language, known as Webster’s Dictionary, was written by Noah Webster in 1828, radically changing some of the British English spelling to more phonetically spelling. For example, ‘colour’ is spelt ‘color,’ ‘Grey’ is spelt ‘Gray,’ jewellery’ is spelt ‘jewelry’ in American, removing extra letters that are not pronounced etc.! Learn the de facto language of the US today, and sound like a native American.