As to Corvette and Chevy in the USA, it has always been considered a part of Chevorlet division as to brand, engineering and engines. Any Chevy dealer can sell them, mainly as a 'halo' car to get the attention of men to buy their family cars. I would note that some Chevy dealers (like Kerbeck in NJ
as noted in an earlier post) tend to be more into sales and service of Corvettes while many only sell 1-2 a year, if any and only by special order.
The Big US 3 are being killed by 'legacy' costs like the legacy airlines face, pensions and retiree health care costs as well as unsustainable pay rates. Hopefully in the next 10-15 years, many retirees will die, and employees hired in recent years will be hired on a more financially sustainable basis. More importantly, the USA will have to have some government run health care as in almost all modern industrial countries for the masses to remove that responsibility and huge costs from businesses.
As me and others suggested, they do need to eleminate a brand or 2, perhaps pare down to Chevy, Buick and Caddy. They need to concentrate certain models to certain brands as Ford and to a lesser extent Chrysler is/will be doing. They need to cut out many dealers. Too many dealers = too much competition among the same brand = heavy discouting = rebates and losses to the parent. Don't forget that GM
pioneered badge engineering, each brand having it's own engines, bodies, features and available in dozens of body styles. Look at the number of brands, wheelbases and body styles GM
offered back in the 1930's to the 1970's to today, and it is a lot less today. They must continue to reduce the numbers of versions and variations of cars they make. They must do more minimal variations of international platforms, they have been moving that way for several years. They must realize what makes people want a Honda or Toyota or Nissan vs. a GM
car and copy that. They must stop throwing so much into horsepower and more into quality, fuel efficiency, quality service and so on.