the selected shipping country is stored in a session named:
eCartCheckoutForm_shipping_country
on the shipping rules, set the triggers:
Session Variable "eCartCheckoutForm_shipping_country" Exists:
AND Based on Session Variable Value.
for US Shipping, Use:
if session variable "eCartCheckoutForm_shipping_country" has a value "=" to "US"
for international shipping use:
if session variable "eCartCheckoutForm_shipping_country" has a value "!=" to "US"