Once upon a time, say, 15-20 years ago, Amazon used to list on all market places items the sellers marked that they would ship internationally. That was when Amazon had only the US, UK, France, and Germany marketplaces. Is Amazon expanded its marketplaces, they became acquiring sellers register in those places. Is also has something to do with taxation laws as well.
Selling across national borders has become more and more complicated.
You can list internationally using the tool Build Int. Listings. With the matter of the clicks your listing would be in your inventory (you have to make sure your product is permitted to be sold in certain countries).
Prices will be in the currency of the marketplace. This means that the UK would be in pounds sterling, US in dollars, France in euros, etc. I believe it is possible to set your own prices in each marketplace.