The Mysteries of Amazon

I am, on the whole a big fan of Amazon. As a purchaser of ebooks I appreciate the sheer variety of Kindle content available. It is, quite simply mind boggling! From the point of view of an author I value the flexibility offered by Kindle Select which enables me to promote my books as free for 5 days in any 90 day period generating interest in my stories. However one aspect of Amazon which frustrates me is the way in which reviews posted in one country only appear in that jurisdiction. My book, Samantha recently received a 4 star review on amazon.co.uk which greatly boosted my sense of wellbeing when I read it. However on visiting amazon.com I noticed that Samantha showed as having no reviews. This is, to my mind bizarre. As a bit of a simpleton I would have thought that as Samantha is available world-wide reviews provided on one Amazon site should show up on all other sites. The same content is available globally so why can not the reviews show up world-wide? Reviews can be a factor in determining whether an interested browser turns into a book purchaser and anyone visiting amazon.com would not be aware that my book had been reviewed in the UK which could mean the difference between selling (or not selling) a copy. I would be interested to hear your views. Kevin