We have a handy guide that shows you how to use Existing Codes. While that guide is about setting a minimum purchase amount, the feature you're looking for is available using the same mechanism by using Shopify's own UI to set up your code.
Similar to the way you could add a minimum purchase amount to a "Predefined Code" you can also set up a custom Free Shipping Code that is only valid in a specific country 😊! Here's how you can do this:
Go to the Discounts section in your Shopify website and click the button in the upper right and click Discount code. Select Enter the discount code you want then select the Free shipping in the Types section. Select the countries that you want to offer your free shipping from the Browse button.
If you still have questions, you may submit a ticket here and we will get back to you as soon as we can.
KEYWORDS:
Is it possible to remove free shipping from other countries?
How do I personalize my Discount codes?