Liberal solution: Just raise he cost of a stamp to $500 and they’ll pay the debt off in no time.
Long ago, in a different life, I carried the mail and worked through the transition from being employed by the United States Post Office Department to being employed by the Postal Service.
The one good thing about the POD was that, at least, it was a constitutional function of USG, provided for by one of the 18 enumerated powers.
I believe they are deliberately slowing service too. I recently sent a letter to a guy 15 miles away from me. It took 14 days. Wow, a mile a day. It was time sensitive too.