Why are some words in English English and American English spelt differently?

Answer 1

since we americans gained independence from Britains(english) we wanted to have our own ways. that is why we decided to change some of the words such as neighbour to neighbor, colour to color etc.

Answer 2

For the same reason why words in Middle English and modern English are spelt differently: Change. Change is the cornerstone of any language. American English came over when the Colonies began, but as the nation grew and changed, so did the language. It's noticable even within the US itself: there's a lot of slang used in the North that you would NEVER hear in the South, as well as different influences from our bordering countries (I find myself using a lot more Spanish-influenced language due to my living maybe 100 miles form the border, and my cousin in New York uses a lot more French due to his vicinity to Canada.).

But for the most part, it's just that the languages evolved over time, in the same way that animals do. African elephants and Asian elephants are a lot different, but they're still both elephants.

Answer 3

because they're different dialects of the same language. In a sense, they've evolved differently over time.