If you only provide domestic shipping or cannot ship to certain countries, you can designate which countries you want customers to be able to select in your Commerce web store.
To designate countries you ship to:
Go to Commerce > Websites > Web Site List.
Click Edit next to the website you want to modify.
On the Shopping subtab, in the Shipping Page section, clear the Web Store Ships to all countries box.
In the Countries Web Store Ships To field, select the countries your customers should be allowed to select at Checkout in the web store.
Your customers can only have orders shipped to the countries you have listed.