USPS is run as a financially self-sustaining business wholly owned by the federal government. (So, not for profit, but also not funded by the government.)

For a long time it was in this weird double bind because the federal government mandated generous health insurance for USPS employees, but did not allocate funds for it, because USPS was supposed to provide its own funds to cover all expenses. It looks like new legislation (PSRA) was finally passed in 2022 to move that burden from USPS and onto the OPM.

So, combining that other thread about Canadian payments, USPS is (the American equivalent of) a crown corporation?