change-default-country-and-state-on-checkout-page.php

/**
 * Change the default country on the checkout page.
 */
function wb_change_default_checkout_country() {
	// Enter the country code here.
	return 'XX';
}
/**
 * Change the default state on the checkout page.
 */
function wb_change_default_checkout_state() {
	// Enter the state code here.
	return 'XX';
}
add_filter( 'default_checkout_billing_country', 'wb_change_default_checkout_country' );
add_filter( 'default_checkout_billing_state', 'wb_change_default_checkout_state' );