I have received my tracking number, but it hasn't been updated.
The good news is that once you receive the tracking number your item is 100% packed. Unfortunately most of the time, the post office doesn't scan the initial package especially for international packages.So technically, you will not see an update until it reaches another facility or sometimes its actual destination,therefore do not freak out (^~^), your item is not lost, it is just in transit and in the hands of USPS.
Some international packages do not have real time tracking information. Sometimes, a package will only show shipment and delivery with no updates along the way.
Once the package leaves the United States, the destination country will generally assign it a new tracking number for their tracking purposes. Unfortunately, this number is not shared with USPS which is why the tracking status is not updated until delivery.