To change the country on a Fire TV Stick, you first need to change the country for your Amazon account. Here are the steps:
Log into your Amazon account.
Go to Accounts & Lists > Manage Your Content and Devices > Preferences.
Click the arrow that’s to the right of Country/Region Settings and you will see your current country.
Select Change, then enter the address you’d like to have associated with your account, and hit Update.
A notification will pop up. Select learn more, then click Update your default Kindle Store or Transfer your Kindle account to.
Now on your Amazon Fire TV, go to Home > Settings > My Account, and choose Deregister.
Finally, you’ll need to register your device by re-entering your Amazon account info for your new country.
And that’s it. Your Fire TV account will now be associated with the new address.