Amazon Appstore can be one of the really good option to get free apps, especially for Android. There are always many such offers daily in the Amazon Appstore, but if you are not residing in the United States (US), you will not be able to get any such apps. Amazon App Store is actually not even available in Canada or Mexico though they are in North America.
Even if you have a proper credit card billing etc., you will not be able to get an app from Amazon Appstore, but it is possible to get any free apps from Amazon Appstore, and here is how you can get Amazon Apps even from outside US:
Step 1: Create a new Amazon account by selecting “No, I am a new customer”, and complete the registration wizard.
Step 2: Put US Address and Phone Number. You can put any random phone number as long as it ha proper code.
Alternatively, you can generate random US address and phone number, etc. with www.fakenamegenerator.com
Step 3: Assign US address as account’s 1-click default address.
Step 4: Next, go to “Add a Credit or Debit Card” section. Paypal provides developers with sets of test credit card account numbers which can also be used in Amazon account. You can also use these test credit card numbers to register in Amazon Appstore.
Step 5: Your Amazon account is now configured to get any free apps from Amazon AppStore
Step 6: Now you can download and install Amazon AppStore for Android. Run Amazon AppStore App and login with this new username/password. Now you can download all free apps from Amazon.
NOTE1: You will still not be able to purchase any paid apps (apps which are not free) with these test credit cards.
NOTE2: It is highly recommended to make a new user rather than using US address in preexisting usernames.