How to reorder address fields for Checkout for WooCommerce.

reorder-address-fields.php

<?php
// Do NOT include the opening php tag.
// Place in your theme's functions.php file

add_action( 'woocommerce_default_address_fields', 'cfw_reorder_address_fields', 100000 + 10 );

function cfw_reorder_address_fields( $fields ) {
	$fields['city']['priority']  = 50;
	$fields['city']['columns']   = 4;
	$fields['state']['priority'] = 60;
	$fields['state']['columns']  = 12;

	return $fields;
}