You may want to see if you can restrict buyer-residence countries at the payment processor's end; I'm pretty sure at least PayPal has this, not certain about Google Checkout.
All the IPN data should be included in the Suspected Fraud email; perhaps you could filter those to be auto-forwarded to another email address where your script would receive and process them? The way our service handles these mismatches is a full stop, don't process the order at all, just notify the seller, so we have no way to transmit the IPN data for Suspected Fraud orders by any other means.
We had briefly supported a new PayPal feature that could callback to our system during checkout to recalculate shipping if necessary, which would also prevent buyers in forbidden countries from completing checkout at all, but there were some bugs at PayPal's end that we could not work around, so we rolled back our support for that feature until PayPal got it better sorted out at their end.