Sent my mom a very small package about 300 miles away via USPS priority. It took 16 days to get there. It took 11 days to get more than 50 miles from us. And that's not my first such story, and I bet everyone reading this in the US has one or more just like it.
Any other business would be allowed to fail. USPS should be allowed to fail. Yes, they handle a lot of packages. Yes, other shipping companies make mistakes too. None of those others have given me even a single story like that, as shipper nor receiver.
And there is no one you can call, no one who will do anything at all to help. You just have to wait until they decide today is the day they are going to pick that box up off the floor and do something with it.