At the cart estimator there is a countries drop-down field, where customers select which country that they would like to see shipping rates for. However, as this store currently ships to only the USA and Canada only those countries should be visible in the field.
Magento has built-in functionality to limit the countries that can be shipped to.
This is located in
System -> Configuration -> General -> "Countries Options"
Selecting only “United States” and “Canada” from the “Allow Countries” multi-select field will limit the quantity of countries from all countries drop-down fields on the frontend. It is also possible here to denote which countries must have a postcode specified.
After saving the configuration only the selected countries will be presented in the drop-down field on the frontend:
Note that this will also limit the countries that can be selected in the customers’ saved addresses:
This also applies to the checkout: