Edit: Wait, that page says they'd still be at -$3B in 2010 without the pre-funding. And it looks like they haven't been paying into it since 2011. http://www.opm.gov/news/testimony/112th-congress/us-postal-s... So I guess I have no idea how profitable they are.
If you give me a government-granted monopoly and a phalanx of federal agents empowered to put my competitors out of business, I'd have to be providing very poor service to be losing billions of dollars. Unfortunately, the USPS has managed to do just that.
They can't add new products without Congress. They are also looking at money services, like basic check cashing, to help the 10+ million US households without regular access to a bank. It could be a great help to many impoverished Americans and, at the same time, boost USPS profits – but it relies on Congress to act. One or two Senators with heavy contributions from check cashing companies could derail, stall, or kill the effort – a net loss to society.
So if you can eliminate Congress, throw out their arbitration rules, they might be able to make the structural and functional changes they need to succeed. This does mean closing offices, distribution centers, and having a pension and retirement system they can afford to offer. Which by the way is what is facing most government employee pensions as many are unfunded and have ludicrous payouts