1. Connect your iPhone, kick start the iTunes and sign out from the default email address (Apple ID) by clicking the email address button in the upper right corner of the iTunes.
2. Go to iTunes Store homepage, scroll down to the bottom and then change the country to United States.
3. Search for Kindle for iPhone in that US iTunes store, and click the “Get App” button.
4. When you see the sign in screen, do not sign in. Instead click “Create New Account”.
5. Register as usual but in the Payment Method Page, click “none” as the method... that means you can download free application only in the future, but it avoids the issue of getting an US based credit card. (I suppose the Paypal will work as well, but I have not tested it).
6. Then enter the US Address and phone number that generated before.
7. That’s it!! You created a iTunes new account with your email as the new Apple ID!!
8. Make sure you click the link in the iTunes Store Account Verification email to activate your account.
9. Now you should be able to download the Kindle for iPhone application and synchronize to your iPhone.
10. Run the application in your iPhone and enter your Amazon account information. And you shall see the Kindle eBook you bought before!!

Notes:

1. Since there is no Whispernet here, therefore the Whispernync may not work. In other words, you may not able to switch back and forth between your Kindle and your Kindle for iPhone, and each will keep track of where you’ve stopped reading. But you can download the books from your Amazon archive and read it in iPhone. Enjoy!!
2. In step 7, I reckon since you don’t need a real physical address to ship anything, so may be all you need is to get any US address and corresponding phone number... even the White House address shall work. Just a thought.