As I understand it (and I'm bound to be corrected here), American spelling has generally maintained the original spelling that was around in the 1600/1700's (with the ecption of new words originated in the USA). They then saw no need for superfluous letters.
We in the military have had a 'superior' attitude to the 'correct' spelling of english words in military papers. This is evident in the past of 'correcting' the "z"'s for "s"'s. Naturally, there is a NATO procedure for spelling and the Oxford English Dictionary is the deciding factor (with some French one for the other official NATO language). I have to side with our ex-colonials however, when I pointed out during a meeting that both spellings using zeds and esses were acceptable, and in most cases the zed ('zee' for you Americans out there) is the first spelling in the dictionary.