Step 1: From the Main Menu, go to Settings

Step 2: Under Settings, go to iTune Store

Step 3: Click on Location

Step 4: Change your Location to United States as shown

Your iTune Store preference should appear as followed

After the settings has been applied, US ATV available apps will appear on your main menu

If your website icon is still hidden after changing iTune to United States, go to Settings > General > Parental Controls and set the app to "Show"