USPS hides 9bn of unfunded pension obligations every year and underserves urban areas to subsidize rural areas.
Mail volume is also generally falling as everything moves to email, so it is getting both less profitable and less critical.
The US is a rich country, we can afford to waste a lot of money and not notice, and of course one person's waste is another person's easier job or subsidized service, but given the ongoing decline in the importance of mail (vs package) delivery, it's not clear that this is a particularly important utility for the government to maintain any more.