Function to modify/change the label and placeholder for address fields in WooCommerce

jp_address_field_filter.php

<?php
/**
 * Removes "Town" from label/placeholder in checkout forms
 */
function jp_address_field_filter( $fields ) {

	// fields we want to look for
	$search = array(
		'billing_city',
		'shipping_city',
		'city',
		);

	// go through each field
	foreach ( $fields as $k => $field ) {

		// if it's one of our fields
		if ( in_array( $k, $search ) ) {

			// make it just City
			$fields[ $k ][ 'label' ] 		= 'City';
			$fields[ $k ][ 'placeholder' ]	= 'City';
		}
	}

	// return the fields
	return $fields;
}
// add_filter( 'woocommerce_billing_fields', 'jp_address_field_filter', 99 );
// add_filter( 'woocommerce_shipping_fields', 'jp_address_field_filter', 99 );
add_filter( 'woocommerce_get_country_locale_base', 'jp_address_field_filter', 99 );