1. You need valid US issued credit card to download US app like Netflix and Hulu

2. If you don’t plan to buy anything. You can use one of test credit card from paypal here.
https://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm

3. Setup fake address in US. You can set anything but State and city must be matched with zipcode

4. Login to your amazon account. Add US credit card and US billing address.

5. Go to manage your content and devices menu.

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6. Click on “Setting”

7. Edit payment method and select US credit card

8. Change country to United state

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9. Restart your kindle fire