Oh! I actually know the answer to this one! American newspaper ads charged by the letter, so a lot of people would eliminate unnecessary letters like the second L in “cancelled” or the U in “colour”. Some of these spelling changes were used so often that they stuck, and now Americans just spell some words differently.
In summary: Americans spell things weird because capitalism
Not sure about the veracity of that, but I do know that Noah Webster (as in Webster’s Dictionary) wanted to create a distinctly American way of spelling and remove “unnecessary” letters, as well as spell words the way they sounded. “Color” sounds like it ends in -or, civilization (rather than the British spelling, civilisation) sounds like it has a z in it, etc. Though, some spelling changes did not take off, such as wimmen in place of women, masheen in place of machine, and languaj in place of language.
