While you can't pin their problems on one thing, I think Chilly460 nailed it pretty good. Honda and Toyota are killing them in car sales, reputation and resale value. Pretty much the reason for Ford and GM killing off nearly their entire car lines. But it's hard to believe Ford isn't making a good profit on cars like the Fusion, which I see a ton of out there on the roads.
Sad to say, but I'm beyond the point of caring. As cars get even more complicated and expensive, and repairs are so expensive that you can't afford to let them go beyond warranty, then I'm done with them. When there's an entire industry established around rebuilding wrecked Hondas, because resale value is still better than typical U.S. based manufacturers vehicles, even non-wrecked cars, then you have a severe problem. Still, I can't see a merger helping either one of them.
I just started work on fixing up my '70 F-350, restoring it and getting it ready to paint. By the time I'm done with it, I'll have 20k invested in a truck that will outlast and outwork anything on the market, at 1/3 the price. That $40k I saved (more, given interest on a loan) will buy me a LOT of fuel..lol