If by Kindle UK, you mean Amazon.co.uk's discussion boards, and by Kindle USA you mean Amazon.com, then what Joyce said previously.
If by Kindle USA you mean KindleBoards, here where you've posted the question, then please know that KindleBoards is independent of Amazon.com or Amazon.co.uk. From the bottom of each page on KindleBoards:
KindleBoards is an independent resource for people who own or have interest in Kindle - Amazon's wireless reading device.
KindleBoards.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. Apart from its participation in the Associates Program, KindleBoards.com is not affiliated with Amazon or Kindle in any other way. Amazon, Kindle and the Amazon and Kindle logos are trademarks of Amazon.com, Inc. or its affiliates.
Many authors who are members here also post at both Amazon.com and at Amazon.co.uk, but KindleBoards is not affiliated with either.
Betsy
KB Moderator