On a side note,
the USPS says if you dont overnight express shipping they don't offer tracking (with worldwide) but the few times ive sent packages overseas, with regular shipping. It still gave tracking, it wasnt that great, but it said when it arrived to customs, and left customs, and than when the actual package was delivered
That was 3ish years ago tho.
Tracking is offered on all 1st class, Priority, and Express packages leaving the US for free
From my experience it is up to the receiving country if they update/transfer the delivery status when checking on USPS.com
Many times it is better to use that countries postal tracking once the parcel has entered said country, which may give more detailed information.
This has been helpful lately, as I used for a package that went to an EU country.
Since I constantly receiving various parcels, coming from the US to the EU, I can confirm that this is correct. Usually, tracking (through USPS tracking services) stops working uppon parcel leaves the states. Parcel tracking resumes (through my national postal tracking service) upon parcel enters my country. Usually tracking is very accurate and I can trace through all the various stages (enter/exit customs etc..). In some rare cases, there are extra tracking updates when parcel enters the EU (through a transfer airport), before reaching the destination country. The only blank spot is the timeslot between leaving US and reaching destination country. Usually, that takes 10-15 days. However, there were instances where I waited 30-40 days before tracking resumed at the destination country. Further, sometimes local postal service is lazy and forgets to scan the parcel at all. I received various parcels, with the last available tracking status update being leaving the states.
17track.net is a very nice global tracking service. It collects tracking information for various postal tracking services all around the world. You just enter your tracking number and returns all the available tracking information that is available through different country couriers.