It looks like the problem might be that the session variable for shipTo is not getting set. This is because you have the set session code on the checkout page. The checkout form on this page posts to the confirm page so your code is not getting executed to set the shipTo variable. To make it work properly you just need to move the code for this on your checkout page to the confirm page:
php:
<?php
if (!session_id()) session_start();
if((((isset($_POST["shipping_country"]))?$_POST["shipping_country"]:"") != "")) {
$_SESSION["shipTo"] = "".((isset($_POST["shipping_country"]))?$_POST["shipping_country"]:"") ."";
}
?>
With this code on your confirm page the shipTo variable should be set and trigger the rule. Give this a try and let us know how it goes.
