The U.S. Postal Service monopoly is unconstitutional* and has caused great harm to the American economy.
The Postal Service has had one profitable quarter since 2006. It has lost $63 billion during that time, averaging around $5 billion in losses each year. (To put this in perspective, the annual budget of the State of Montana is less than $5 billion).
The “Service” lost $2.1 billion in the most recent quarter, and expects to lose another $6 billion or so this year. See here.
The USPS has EVERY ADVANTAGE in the marketplace, yet cannot make a profit. In an age when technology is driving engineering to be ever more efficient, the Postal Service continues to use outdated models of processing and delivery.
Now the USPS is seeking to alter its regulations so it can raise its prices faster than the rate of inflation. (See the above link.)
* The Constitution has a provision (Art. 1, Sec. 8) allowing Congress to “establish Post Offices and post Roads” but elsewhere makes clear (through, example, the due process clause, the contracts clause, etc.) that there was to be no government monopoly on delivering mail. The 1st amendment freedom of the press also seems to prohibit the government from controlling the market for shipping newspapers and printed matter.