I'm not aware of any organization that has the same requirements to fund its future pension obligations that the USPS has. That requirement was created by Congress as part of a sustained campaign to damage the USPS.

It seems like your argument is actually that Congress should rescind that requirement, so that USPS can afford to better service urban customers while continuing to be a critical lifeline to rural areas.

Well, if postal services were provided by normal private companies, then there would be none (or less) of that kind of political interference you are complaining about here.