When I buy at Amazon, it’s usually at amazon.co.uk, as I live in the UK. I may buy at amazon.fr (and did when I lived in France), amazon.de (for my family) or amazon.com (to send to US friends).
However, when I click on a blog link that directs me to an item at amazon.com (most of the time), I have to manually change the url from .com to .co.uk to arrive at the corresponding item on the UK site. This only works because of Amazon’s unique identifiers and common URL scheme—otherwise it would require going to the .co.uk (or .fr, .de …) site and using the search function.
The unique IDs and common URL scheme show that it would be pretty easy for Amazon to provide links to the other Amazon versions right in each item’s entry.