Hi there and welcome to the site.
According to Amazon, Snuff is being released on 11th October in the US and 13th in the UK. As you say, it's released on the 22 November in Canada. This happens sometimes with book releases for one reason or another.
Have you considered ordering from Amazon.com? The Americans are getting the same cover as we are this time around.
I buy Bernard Cornwell's books and his latest book, which came out a couple of days ago here, isn't out until next year in the US.
It's a publishing thing.