Differences in American and English/rest of the English speaking world spelling are not only by common usage but by conscious choice, the u was dropped from words like honour and flavour by Webster on purpose. The ending -ize instead of -ise in some words (centraliz/se) is actually older form, and it's the English who decided to replace z with s at some point. I have no idea where the aluminum vs. aluminium originates as they are also pronounced differently.
whoa, the comments were following a fairly innocent linear course when 'blam' it got hijacked into a flamer.
BTW yes our language is always evolving, major change in society drives these changes
e.g. America gaining independence from the Brits split the language assunder (the Yanks are very active in making changes in both spelling and pronunciation), now the internet and instant global communication is driving new changes.