Amazon has a bad track record for international deployment of anything relating to billing. Amazon Flexible Payments Service has been around ages and is still US only. Their Honor System didn't make it out of the US either.
PayPal has its issues but they've always been useful for the large international diaspora of US dealing but non-US dwelling wannabe Americans.. :-)
I'm not particularly enamored of Amazon's international deployment for anything. In Europe, for instance, they only have stores for Germany, France, and the UK, and each of those sites is available only in that language. So if you're elsewhere, say Spain, or Italy or Slovenia or something, I guess you just try and get by with whatever language you know, which is most likely English. But there's something lame about them not just simply shipping from the place most likely to get you your products in a timely manner, as they do in the US. In other words... what they have works, it's just fiddly and not very pleasant to use.
OTOH, as a company they seem a lot less evil than Paypal, so I'll be rooting for them.
They also split affiliate programs so that I can't include links for UK and US folk, say, that will simply take them to the most appropriate store I have to provide 2 links or do acrobatics sniffing IPs and whatnot.