Can't blame the European Union for that then can we? The Germans still use the "British" system but I don't know about the French, someone told me their ambassador to Britain won't even speak in English if they can avoid it.
Its got nothing to do with speaking english does it!As a matter of fact the Americans spelling of words is a lot better than ours,ie color instead of colour,thats just one example,but nothing to do with the topic.
If, as wiz-king says "we have changed out of politeness.(or watching too much US television!)" it's a reflection of THEIR use of the English language and OUR (incorrect) perception that we should modify our use of English terminology.
Why should we change?
Or do you travel across England in an automobile or by railroad train, for example?
I think you'll find "English" is the most bastardised language in the world, as it has roots in more than one base language, and imports from many more around the world.
That's why it has so many words, often two for the same thing, from different sources - and more words by far than other languages. And it's why pronunciations are so odd, coming as they do from different roots.
We've had this topic before and I got the impression that we had decided that American English has stayed much the same as it was when they sailed on the Mayflower. Whereas the spellings of our version of English had changed in Britain..