First off, let me say that I have shares in both GM and Ford, so I will be personally affected if the Big 3 automakers go broke.
I still say "let them go broke."
What would it mean to Ontario and Canada if that happened? Would all the jobs and auto manufacturing disappear? Of course not! Anyone who says otherwise is either foolish or purposely misleading.
Scenarios After they Go Broke
They declare bankruptcy, rip up their union contracts, close un-productive plants, then continue to make only the most profitable and successful lines of cars.
2. Sell off Assets.
GM, for example, could call itself Chevrolet, and make just Chevrolet models, and sell off Buick, Hummer, etc. to other parties. Ford and Chrysler could do similar things. Maybe Shelby would put together some investors and buy Dodge. Whatever happens, we would have maybe a Medium-Sized 10 instead of Big 3.
3. Many other possibilities.
Look, people in the U.S. and Canada will continue to want/need cars and trucks, and wherever there's a need, the free market will step up and provide.