(writing from the USA, Virginia, btw, near-ish to where Elizabeth I sent her first colonizing explorers... I'm not far from the Elizabeth River).

As for American vs. British spellings...

I think it's just an evolution thing. When the first colonists came here from England, the language didn't have any standard spellings. I think that came about 100 years later. Those on the right side of the Pond chose one option to become standard, those on the left, another.

Sort of like the evolution of different finches in the various Galápagos Islands.