There are two ways you can disable international shipping on eBay listings.
Don't include any international shipping options in your listing options template. This is the best method if there are certain product types you want to allow international customers to be able to purchase.
For example, Wizards of the Coast has a policy against shipping in-print sealed product internationally. To comply with this, you could create a listing option template for sealed product that has no international shipping options available and use a separate template for your single cards that does have international shipping options available.
2. Disable/restrict international shipping in your eBay account. This solution involves changes the shipping settings directly in your account on eBay.com. You can do this by following these steps:
In My eBay, go to Account > Site Preferences
Scroll down the Site Preferences page until you see "Shipping Preferences" in bold
Under this section, find the "Exclude shipping locations from your listings" pref and click the 'edit' button next to it
This will bring you to a page that lists the different regions, where you can check the boxes next to the regions/countries you don't want to ship to.