GM and Ford seem to think that the only market is for SUVs and trucks. If you want a sedan, you have to go with the Japanese, Koreans, or Europeans.
Basically, it's the fuel efficiency standards that have driven GM and Ford out of the sedan business. The complex factors are this:
1. In order to meet the U.S. fuel efficiency standard for cars, these companies must sell a large number of compact cars to drive up their average fuel efficiency ratings for their combined fleets of compacts, mid-sized cars, full-sized cars, etc.
2. With UAW labor, these companies can't price their compact cars competitively. Interestingly, their biggest competition for Ford and GM compact cars isn't compact cars made by foreign companies, but mid-sized cars and small SUVs made by Ford and GM. A UAW-made compact car would be priced at $25,000 (for example), so the typical customer realizes that they'd rather just pay another $5,000 to $7,000 for a bigger/better car, or another $10,000 for a small SUV.
3. Since Ford and GM would have to sell the compact cars at a loss just to meet the average fuel efficiency standards for their car fleets and/or make them in Mexico and China with non-UAW labor (and cause major labor strife in the process), they figured it was easier just to get out of the car business entirely.