I'm tempted to say that most american cars since the 70s would fit this thread.
There have been some crappy cars made since then, that's for sure. But the 70's had some real lemons, too. Chevy Vega? AMC Gremlin? Ford Pinto/Mercury Bobcat? Cadillac Eldorado?
Most of these tend to be overshadowed by the horrible cars of the 80's (Chrysler K-cars, anyone?), but I've owned more than my fair share of completely crap-tastic cars from the 70's.
But remember; this thread isn't about crappy, it's about ugly. There are a few decent looking american cars from the 70s, but barely worth noting, and from the 80s it seems things went horribly wrong.
Basically, I'm having a hard time thinking of a good looking american car made after the days of the original mustang and the likes.
I think it depends on your sense of style. The Mach 1 Mustang, for example, is pretty cool, but at the time I thought they were horrid bloated examples of automotive design.
Ironically, there were some really neat mechanical improvements that came on the market in the lost decades, but most of those were hidden behind awful bodywork.
Personally, I think the resurgence of American car style started in the early 2000's. Corvettes lost the slab-sided 80's look and began to look sharp again, Dodge rolled out some nifty trucks and SUVs (Ram, Durango, Dakota), and Ford started to fix the Mustang.
