When the correct Label/Barcode is on the package then you can track all the way. I did this recently with a replacement screen, the first got lost in space.
I've had the same problem, as on your thread on LFPI. When the wrong label is used tracking stops at the departure point. This is not your fault at all it's USPS, or maybe it's fraud at the departure point.
I worked for the UK Post Office back in the early 70's and even then before computers, a special delivery item with a tracking code could be traced right to the point it was lost.
My experience with tracking etc is that it works exceptionally well, but there are a few items that get lost. I worked in the precious metal industry for 20+ years & both companies I worked for sent hundreds of parcels a day usually containing precious metal items or cash but we only had a few go missing maybe 6-8 a year, and the UK Post Office was extremely good at compensating in full, after about 6-9 months.
Unfortunately USPS aren't so good at accepting responsibility.
Ian