I've checked with Amazon and as for the purchase of the Kindle itself, it can be purchased with a non-US issued credit card but the item has to be sent to an address in the US.
For the purchase of content, they say it has to be linked to a US issued credit card.
I live in Singapore and intend on getting a Kindle. Lucky for me my postal service here has a service where they will provide us with an address in the US and then ship it out to us here, so that's what I'm gonna do when I purchase my Kindle. As for content, well there's so much free stuff out there for me to upload to my Kindle, I don't think I'll be purchasing any content from Amazon any time soon but I will give the gift card route a try.