Bragman said that while GM would stand to gain market share by merging with Chrysler, the new combined company would also lose money because it would have similar models, like the Dodge Ram and the Chevy Silverado, competing against each other for buyers.
D'Aveni said that the historical strife between the two companies also doesn't help the prospects for a successful combination.
"You've got to manage the culture of two enemies that have hated each other for decades," he said.
But Van Conway, the president of the turnaround firm Conway, McKenzie and Dunleavy, said he wasn't ruling out the possibility that a merger could help GM.
The new, combined company, he said, could save a substantial amount of money by eliminating overlapping positions.
"That's why two losing companies typically merge, not because of revenue. They merge because of the reduction in overhead costs," Conway said.
In determining whether a merger would work, he said, the automakers would have to weigh those savings against other costs, including severance for laid-off employees. The companies, he said, might also not want to deal with the diversion the merger would cause for top management at an already challenging time.
Merger or not, there still appears to be a least some hope for U.S. automakers.
Bragman said that when it comes to fuel-efficient and attractive passenger cars, both GM and Ford are catching up to their foreign competition.
Sales for GM's 2008 Ford Malibu, for instance, "are through the roof," thanks to a more stylish design and better fuel economy, he said.
Bragman said the companies are also working to improve their auto plants so that they can make different kinds of vehicles on the same production lines, much like Toyota and other foreign automakers that have newer facilities than GM's and Ford's.
For now, he said, the companies have to contend with a more immediate concern: whether they'll have enough cash on hand to survive the current financial crisis. Within the next two years, he said, both companies could face insolvency.
"It's a vicious cycle," he said. "They need to be able to raise more cash in order to operate, but their ability to raise that cash keeps getting downgraded by Wall Street."
Congress passed legislation earlier this month to provide U.S. automakers $25 billion in low-cost loans to upgrade older production facilities, a move that Bragman said represents just "a drop in the bucket."
GM and Ford, meanwhile, each say they're taking their own steps to return to profitability. Both automakers have touted their new fuel-efficient models and are seeking to cut costs.
In June, GM announced that it would close manufacturing plants in Moraine, Ohio; Janesville, Wis.; Oshawa, Ontario; and Toluca, Mexico. ABC News affiliate WZZM reported Monday that the company is also closing a stamping plant in Wyoming, Mich.
Meyerand said GM is trying to raise money by selling its closed facilities as well as its Hummer brand.
Ford has said it would convert three of its North American truck and sport utility vehicle plants to small-car production. Ford also offered buyouts to 54,000 hourly workers earlier this year and laid off hundreds of white-collar workers during the summer.
If the efforts don't work, and if the companies look likely to fall into bankruptcy, Bragman said he expected the government would step in with some sort of assistance.