It's good news, bad news time.
The good news is that I have The Nice Google Checkout plugin setting flat rate shipping to allow for international buyers. Heck, you can even set it to include different rates for different countries, exclude some countries from some rates and use the same rate for multiple different countries. So, overall the shipping rate feature is much more robust than it was before.
Now for the bad news. The bad news is that currently, the international shipping rate does not increment as more items are added to the cart. Which, in my humble opinion, is less than desirable.
I think I have worked out the details for incrementing the international shipping rates on a per item basis. However, it is going to take me more time before I have perfected the code.
Sorry for the delay.
~ All the best