The issue isn't the USPS, it is the chains that Congress placed on them and refuse to remove.
The USPS cannot price it's services without approval from Congress regardless of profitability. (FEDEX/UPS have no requirement)
Congress MANDATES that the USPS deliver mail to every address in the US 6 days a week, even in the bottom of the Grand Canyon so every day the USPS mule team carries mail down into the canyon and brings mail out and has to maintain the cost of the mules and personnel. (FEDEX/UPS have no requirement)
Congress mandates that 1st class mail must be delivered, within I think 3 days, with required the USPS to design and purchase hybrid OCR/sorting equipment to the tune of many millions of dollars and Congress additionally mandated that if these OCR/sorting equipment breaks, the USPS only has a few hours to get it back up and running. Since these OCR/sorting machines are one-offs, the parts are so expensive there is a critical parts center in the Indiana to securely store the parts and there are jets standing by to fly replacement parts anywhere in the country which means the care and feeding of the planes. (FEDEX/UPS have no requirement)
Congress mandates funding levels for the USPS retirement fund much higher than private companies which causes a huge cash flow drain on the organization. (FEDEX/UPS have no requirement)
The labor unions drive much of the issues the USPS has to deal with and with a very low margin product/service pennies count.
Congress will not allow USPS to diversify services, like ebillpay etc. I wash helping USPS put these things in and UPS and the banks cried to congress and congress shut us down.
The list is long but I think you get the idea.
So, true USPS could use some efficiency/organizational work, but congress is the biggest obstacle to the USPS being successful.