GM should have been told in 2005 that there would be no help coming.
Bush should have warned them in public. No one would have lent them money or bought their bonds. Then they'd have had to file and then new owners such as Penske or Kerkorian might have come in and basically wiped the books.
Private money would have been the ones taking the risk. If they couldn't make it, well, then, either someone else comes in or it closes the doors and people buy more Fords, Chryslers, Teslas and ToyHondas.
The UAW would have been TOTALLY screwed, which would have been tragic for some of their members, but better for the country that the organization would have lost so much credibility with workers.
The govt would have had to pay benefits for a lot of folks but most of the jobs would have probably come back with the new owners. And look what we've done instead: Over $50B spent for a company with 1M retirees and 202k employees. That's like $40k PER PERSON SPENT ALREADY, not even counting the $42B tax breaks.
Instead, we propped up this lame company, subsidized its bankruptcy with the govt as owner, made everyone mad at it, own shares of a pile of garbage we'll never be able to sell, and we are still stuck with a lame company.