The benefits of joining Amazon.com as opposed to your own countries are quite significant. You can buy kindle books from different countries sites and save money, and you can send kindle books as gifts, which is lucrative for American authors, not that I am having a go at fellow writers in the US of course, but the ways of Amazon are bizarre to say the least. A link back to your own country's site instead of a 'Buy with 1 Click' button, and no 'Send as a gift' button either. According to a colleague across the way her Christmas sales increase whereas mine will be under the thousand monthly sales total for the first time ever since I published last May.
It is of course swings and roundabouts though as being a Brit ex-pat my royalties are only taxed by the Philippines, but US ex-pat authors are taxed twice, by the US as well as the country of residence.