WooCommerce - Do not allow the user to select the 'default' country

// WooCommerce - Do not allow the user to select the 'default' country
add_action( 'woocommerce_after_checkout_validation', 'custom_validate_country', 10, 2 );
function custom_validate_country( $data, $errors ) {
  if( 'default' == $data['billing_country'] ) {
    $errors->add( 'validation', 'Please select a billing country' );
  } else {
    if( 'default' == $data['shipping_country'] ) {
      $errors->add( 'validation', 'Please select a shipping country' );
    }
  }
}