Originally Posted by abookreader
Buy your gift cards out of your German Amazon Account, email them to your German email address ... and then go into your US Amazon account and apply that Gift Card number to your US Amazon account. That is how you will pay for your US Kindle books.
I cannot confirm this.
I tired just that a few minutes ago (tested it with a 10€ one and actually found this forum when searching for some feedback).
Amazon.com tells me this:
We had a problem redeeming your gift card
There's something wrong with the gift card claim code you entered. Please check for transposed digits, omitted digits, and similar errors. Don't worry, this is not case sensitive.
Tried it both with my normal account as well as with a fake US one I made.