If you want to get one of those that are available in the US only (like the new paperwhite or HD), then you can use
www.shipito.com or
www.usunlocked.com. Both provide you with a US address US only Amazon items can be shipped to and they ship items to you from their warehouses at very reasonable rates. If it is just to get a Kindle registered to a US account, then there are easy ways to re-register your existing Kindle, as mentioned above.