That was very interesting ! I knew about the French influence in words in "-er/-re" and "-or/-our", but not about the historical context. I also didn't know that "-ize" was the usual form in UK till the 18th century. I guess it doesn't really matter which one one uses.
This site gives similar explantations, with also the difference between "programme" (UK) and "program" (US) - the first is the original in French, Latin and Greek, so the American version is just a simplification. For "pyjama" (UK) and "pajama" (US), the Hindi and Persian roots give reason to the latter. Note that French also spell it with a "y" (and pronounced it like in "pit"). I guess the word first came into the English language, where the "y" is pronounced "e", then came with this spelling into French who have pronounced it like it was written (as all French vowels only have one pronouciation). But it may have happened the other way round too.
I would like to point at the link between AmE and Japanese English as well. As explained on the same site (phonology section) some Americans tend to pronounce some short "e" sounds (like in cut or rung) and short "o" sound (box, hot) like "a" (such as the final of "sofa"). I guess that's why Japanese people, heavily influenced by the US after the WWII, have adopted English words like "coktail" saying "kakuteeru", "color" saying "karaa or else "cover" pronouced "kabaa. They could have spelt them with a "o" instead. That would have made them easier to understand for foreigners and closer to international English.