Actually, British English was freely exported before the Revolutionary War, and even afterwards, with the most famous export being the set of lead printing plates of the Bible that were actually passed through the naval blockade that was part of the War of 1812 to the Philadelphia Bible Society, and are the basis of all "King James" editions of the Bible in this country. (The fact that the edition is not the "original" authorized version of 1611, but is, in fact, the 1769 Cambridge revised edition somehow seems to escape the "purists" and "thumpers.")
It was Ben Franklin that changed everything about American spellings. He even proposed an entirely alternate alphabet, but it never took off; the legacy is in the common words like those listed above, that lost double vowels and changed consonants.
Yes, I know - the above quoted post is tongue-in-cheek. But at the risk of someone taking it seriously, here are the links. The first is the transcript of Franklin's actual letter, and the second is the explanation of his proposed system, later championed by Noah Webster, although never universally adopted, as set forth in the third link:
http://grammar.about.com/od/readingsonl ... anklin.htm
http://www.omniglot.com/writing/franklin.htm
http://grammar.about.com/od/words/a/Noa ... elling.htm