This may help
I will offer what I do but you may be better served to do some reading and familarize yourself with this forum. There are a number of threads pertaining to this situation and possible solutions posted on this forum.
1) Open a new account on Amazon.com using your U.S address, make sure your country is specified as U.S
2) Download kindle pc/mac app for your computer.
3) I use a hide ip program so as my ip show as U.S and download to my computer and then transfer to my kindle with usb
Some folks don't bother with the hide ip but I rather be as discrete as possible.