Free shipping for international orders

I want to use Google Checkout as payment method on my shop, and since it doesn't offer carrier calculated shipping rates fro international orders, I want to enable free shipping for orders outside USA and to handle shipping costs for those manually, while for USA orders I'll keep my carrier calculated shipping costs.

In theory, it looks fine, but I didn't managed to have free shipping zone-based.
I enabled freeshipper with a Shipping Zone "Non-US" who include all other countries, but in checkout I still see my other shipping methods instead of free shipping. My products are real, I can't either setup them with 0 weight or always free shipping because this will break shipping cost inside USA.

So, my question is how do I enable free shipping if the customer is outside USA, without any other restriction like order value etc?