On international shipments with USPS, you have to fill out a Customs Form.
This customs form has a number (I think the are presently starting with the letters 'CP' at the moment) and this IS trackable on USPS.com.
International shipments of Global Priority or Global Express come with an automatic $100 insurance - of course, you can buy more.
Shipping to an APO/FPO (Army Post Office / Fleet Post Office) is treated as international shipping - Customs form must be filled out, etc..
There is GREAT APO/FPO info here:
http://www.shipitapo.com/info/apo_fpo_guide.php
I stopped send to APO/FPO's, because there is *NO* confirmation available, no tracking once it leaves the US itself, and really no guarantee it gets there. Once it hits the proper US military post office in the US, it's out of the USPS's hands, and in the military's hands.