Merging GM and Chrysler is a bad deal for everybody involved in the automotive business and NASCAR.
They compete in basically every vehicle segment and have the same strengths (trucks, SUVs, large RWD cars, and V8 engines) and weaknesses (cars). GM would have to shell out billions buying out duplicate employees, plants, dealers, and brands. The only benefit to GM would be minivans and Jeep.
It wouldn't be any better in NASCAR. Once again GM would cancel one (Dodge) since it doesn't make sense to split the money between 2 brands and compete against yourself. That's why GM dropped Pontiac, Buick, and Olds from NASCAR.
Daimler screwed Chrysler over big. When they "merged" Daimler was bleeding money and Chrysler was very profitable. They took Chrysler's money to rebuild Daimler while leaving nothing for Chrysler to continue their future development.