woosurcharge.php

<?php 

/*
Plugin Name: WooCommerce Order Surcharge
Plugin URI: https://www.karks.com
Description: Adds a flat surcharge to every order. Based on WooCommerce Snippet: https://docs.woocommerce.com/document/add-a-surcharge-to-cart-and-checkout-uses-fees-api/
Version: 1.0
Author: Eric Karkovack
Author URI: https://www.karks.com
Code culled from https://docs.woocommerce.com/document/add-a-surcharge-to-cart-and-checkout-uses-fees-api/
*/


/**
 * Add a standard $ value surcharge to all transactions in cart / checkout
 */
add_action( 'woocommerce_cart_calculate_fees','wc_add_surcharge' ); 
function wc_add_surcharge() { 
global $woocommerce; 

if ( is_admin() && ! defined( 'DOING_AJAX' ) ) 
return;

$county = array('US');
// change the $fee to set the surcharge to a value to suit
$fee = 1.00;

if ( in_array( WC()->customer->get_shipping_country(), $county ) ) : 
    $woocommerce->cart->add_fee( 'Processing Fee', $fee, true, 'standard' );  
endif;
}