GM is not the largest bankruptcy ever in the USA. GM is the largest Industrial Sector bankruptcy ever in the USA.
It might be a better perspective to list the hierarchy of the largest bankrupt entities in the USA in light of the GM bankruptcy:
(1) US Federal Government,
(2) State Governments,
(3) County Governments,
(4) City Governments.
Many observers point to GM's bankruptcy being a function of Poor Management and a Unionized Work Force. Could one then make the argument that all forms of US Governments are run by Poor Management and function with a Unionized Work Force hence leading to bankruptcy?