You may need to change your accepted delivery Countries in magento to restrict where you will accept orders from
This is a very simple process and will affect your whole website in seconds, no need to change each product,
You need to log into the back end of magento - select "system" - "configuration" - "General" Tab. The top section of the general tab will be "General and it is here where you can change these
In default country - as the name suggests you need to select what you want to show as default when customers get through to the checkout
Allowed Countries - this is where you select the countries you will ship to and anything here selecting in grey will show in a list on the checkout when choosing country. You can have 1 allowed country by simply clicking and it will turn grey. Alternatively for multiple counties you can hold down the "Shift" button on your keyboard and click to select / deselect multiple options.
Hit save when done and your configuration will be live on your site immediately