[tzs]

It's not really accurate to say the US is the one doing the morphing. Before the early 19th century, both spellings of most of these words were acceptable in the UK and the US, because these words came into English both from French and from Latin. It's more accurate to say that the UK and the US, when each settled on one of the two spellings as standard, chose to settle differently.

This standardization in the US was greatly influenced by Noah Webster and his dictionary. He tended to go with the spelling variant that fit more with how the word was pronounced. His dictionary was influential enough to make those spellings dominant in the US. Those spellings then came to be seen as Americanisms in the UK (even though they had long been acceptable UK spellings...), and so the UK standardized on the other spellings.

Webster was also an advocate of spelling simplification, and was responsible for dropping the 'k' from 'musick' and 'publick', and those were picked up in the UK.

See: http://www.livescience.com/33844-british-american-word-spell...