Hi epigene,
I've been thinking about what you said and realized that I actually purchased a kindle book myself, with a Japanese credit card and from Amazon.com (April 20, 2011). I don't actually have a Kindle but I read it on my mobile phone app. My mother has a Kindle though and she is able to purchase books from Amazon.com on her Irish credit card (recently). I think the Kindle will arrive today but may be nobody at home when the postman arrives...