Why are words spelled differently in American English and British English?

Ever since Noah Webster published the first dictionary of American English in 1828, Americans have spelled some Words with fewer letters than the English have, such as "color" in place of "colour," or "program" in place of "programme."

It should be pointed out, though, that in those days probably even more than now, not everybodty learned the accepted spelling in his own country and his own time. If you look at the original versions of Shakespeare's works, you will find that even he did not always spell the same Word the same way at different times.

But back to Webster. Most likely he figured it was a fresh start, and he might as well eliminate letters that did not seem needed to communicate the meaning.

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Standard spellings in Britain started in the 18C, but what's rather odd is that although many American spellings shorten Words, US colloquial use appears to like lengthening them with stretched suffices. For example, turning the adjective "inspiring" into "inspirational", or the verb "burgle" to "burglarize". That "z" is the suffix also more common in American than British English.

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Might Webster have also been catering for the fact that the USA had grown very rapidly - within a couple of centuries or so - from a polyglot stream of settlers from many European countries with their own, very different languages?