the shipping country is stored in a variable named:
WA_getSavedFormValue('CheckoutWizard_Cool_Default','Country_2')
on the confirm cart page, add a set session value server behavior (on the server behaviors tab, click the plus button, select eCart -> general -> Set Session value
set the trigger to any form post
set the name to:
Shipping Country
for the value enter:
<?php echo(WA_getSavedFormValue('CheckoutWizard_Cool_Default','Country_2')); ?>
the in your shipping rule use the trigger:
session value ShippingCountry is not empty
AND
Session ShippingCountry is = to US
for the US flat rate
and
session value ShippingCountry is not empty
AND
Session ShippingCountry is != to US
for the international flat rate.