Spelling in American English was highly influenced by reformer Noah Webster.
http://www.notablebiographies.com/Tu-We/Webster-Noah.htmlIt was Webster that first proposed changing the traditional spelling of commonly used words to simplified versions based on their pronunciation* (phonics). Center instead of centre, plow instead of plough etc. This would in his view make them easier to spell & understand although as a committed federalist he also did it for the sake of being different. His first dictionary entitled "An American Dictionary of the English Language" contained the simplified versions of many English words. It was first published in 1828 & was later adopted by Congress as the American standard dictionary. Traditional English spelling is influenced in the same way by the "Oxford English Dictionary".
Unfortunately (my opinion) American English is rapidly taking over as the International standard mainly due to the fact that it's the international computer language. If you work with computers you're forced to learn & use the American spelling whether you want to or not. This is also highly influenced by 'Hollywood' which produces a large proportion of the films & TV programmes shown throughout the world.
There are also basic differences in American & traditional English grammar. Again, the American version is rapidly becoming predominant. I don't know if Webster was behind this or not as he wrote other books on the subject of spelling & grammar.
*If Webster had had his way this would have been taken much further. His "Collection of Essays and Fugitiv Writings" (1790) encouraged "reezoning," "yung" persons, "reeding," and a "zeel" for "lerning". In fact he could be called the father of txt spk.
