>Bill Bryson's Made In America

I'm pretty sure that the book you need is called (here) "Mother Tongue" by Bill Bryson. I re-discovered it recently after a year or so of its absence, when I moved a bookcase and found it down the back. Slippery chap that Bryson, you can never find him when you need him.

In the book he puts forward a quite convincing argument about words like "gotten".

I quote from p164 of the UK Penguin edition:

"It is certainly true that America in general preserved many dozens of words that would otherwise almost certainly have been lost to English. The best noted, perhaps, is gotten which to most Britons is the quaintest of Americanisms. It is now so unused in Britain that many Brtons have to have the distinction between got and gotten explained to them even though they make the same distinction between forgot and forgotten ...."
Imagine that!