If the uk writes a word different from the us, that doesnt only affect the uk (and its commonwealth) but it could affect everyone that is learning english (partially depending where you are from and what you are exposed to. When in europe and don't watch a lot of movies you will probably now solely british english. When you're from the americas and watching a lot of series and movies you probably are more inclined to american english)
Just saying, it is not just one small country that deviates from the usa with its words. It affects the rest of the world that learns english aswell (both through schools and exposure).
I personally watch more bbc than I do any local channels so I ve been exposed to a lot of british english.