Add states to countries that do not include states in WooCommerce core

custom-country-states-woocommerce.php

<?php
/**
 * Add custom states to country in WooCommerce (Ex: Bangladesh)
 */
add_filter( 'woocommerce_states', 'BD_woocommerce_states' );
function BD_woocommerce_states( $states ) {
	$states['BD'] = array(
		'SS' => __( 'Barandipara', 'woocommerce' ),
	);
	return $states;
}