I don't see why the US Postal Service can't have tracking on International shipments. I've started suggesting Priority International, especially the Flat Rate Envelope and Flat Rate Box. Now I find this small print in the US Postal FAQ. No Tracking on Flat Rate Envelopes and Flat Rate Small Box. This is so frustrating.
Online Tracking - Put our delivery information to work for you. Track PMI package shipments. Note: Tracking is not available for Priority Mail International Flat Rate Envelopes or Priority Mail International Small Flat Rate Boxes.