WooCommerce - Set default state/country for checkout

gistfile1.txt

/** 
 * Manipulate default state and countries
 * 
 * As always, code goes in your theme functions.php file
 */
add_filter( 'default_checkout_country', 'change_default_checkout_country' );
add_filter( 'default_checkout_state', 'change_default_checkout_state' );

function change_default_checkout_country() {
  return 'XX'; // country code
}

function change_default_checkout_state() {
  return 'XX'; // state code
}