British vs American spelling?
It's not that simple.
I'm British, despite the Polish surname (father was one of the Polish RAF pilots in WWII), and when I was at school in the 1950s and 60s it was "organization"; which is still the preferred spelling in the Oxford English Dictionary, - despite the Media spelling it with an 's' instead of a 'z'. What you may not be aware of, being on the other side of the 'pond', is that Oxford is fighting something of a 'rear guard action' against the ever encroaching 's' and the disappearance of the 'z'. Being a Northern England inhabitant I also find the stronger 'z' more sensible from a pronunciation point of view than the softer 's' of the South.
I remember that it was not until the mid 1970s that some people started to tell me that I was using the American spelling. In fact most British people that I meet, including my students here at the university where I teach, believe this to be true. Hell, the whole continent of Australia believe the 'z' is the American spelling!
Well at nearly seventy, I shall continue to spell all such -ize words with a 'z', if only because I see young people not even attempting to pronounce my name because it has a 'z' in it! :-)