I'd agree. I wish US made cars had Euro-spec options.
Look at it this way. Ford, GM (did), and Scion all offer manufactured aftermarket parts, so obviously there is enough of a market out there for these special parts, but not enough of a market to install those parts on a few cars that roll of the line?
I'll still buy a Fiesta, but if Ford doesn't release a sportier model in the states, than I'll just have to build my own. That's money that Ford isn't making.
I also think that sportier models tend to keep the values of normal models a bit higher as well. The SVT Focus still demands a pretty penny, and I see many kids attempt to make SVT's out of their ZX3's. Corvette guys get Z06 wheels to try and mimic that crowd. Hell, even Mitsubishi used the Evo as a way of selling the Lancer Rally Art. Personally, I think the Lancer would be gone by now if it weren't for its hot older sister.
While I agree that first and foremost you've gotta sell cars, the reason many enthusiasts won't buy a new car is because it's just not worth it. It's not worth buying a brand new hatchback that gets 30mpg, has a crappy boring interior, crappy suspension, and looks like an egg. I'm sure my girlfriend would have no problem dropping $15,000 on such a car, but I'm a buyer who you'll lose because "going new" just isn't worth it.
If the manufacturers want to sell cars, they'll make new cars worth the money.
I'd easily pay $18,000 for a sporty, 35-40mpg hatchback, but it needs to be worth my money...otherwise that 5 year old cars of another manufacturer will come first.
It doesn't have anything to do with the brand of the car either. I'd rather buy a used S2000 over a new Miata, a new Fiesta over a used Camry, a used Corvette over a new 350Z or a 90's luxury cars over almost all of the above. That's mostly because we as "educated" consumers are going to buy whatever is the best deal, biggest bang for the buck.
As I understand it, aside from older Honda Civic SI, a very used MINI, a ZX3 (sorta), and a few other odds and end there is no 35+MPG "sport-tuned" hatchback on the market. That's the car I want to buy, everything else is a sacrifice.