Um, none of the cars you mentioned are available in California, let along US... So you can't compare them. They're apples and oranges. (Plus, I highly doubt your claim that they are cheaper and cleaner. Diesels in Europe can't yet meet CA emission rules, and cars are EXTREMELY expensive in UK, I know cuz I'm in UK right now! And did I mention these cars are tiny sub-compacts vs a mid-sized Prius?)
Though I absolutely agree with you that the Prius is not the ultimate solution, but as it stands, the Prius is the most fuel efficient, cleanest all around vehicle available to the American consumers, period. So if one's goal is to have a vehicle that serves the needs of most families while providing the best mpg and lowest emissions, the Prius is the best choice. And at a low $20K, which is below the average new car transaction price these days (I think around $27K) it's really NOT expensive at all.
Again, I wouldn't buy one because like you, I value performance and style over a little savings in fuel and emissions. But that's beside the point. (I'd buy a stripped down Civic before I'd consider a Prius. It makes more sense from a value stand point.)
The Volkswagon Polo Blue Motion (Diesel) scores a 99 on the UK's CO2 emissions test, while the Prius scores 104, making the Polo cleaner than the Prius. The Mini Cooper D scores a 104, which is the same as the Prius. Both the Cooper D and Polo have better gas mileage than the Prius. All cars are ridiculously expensive in the UK because of their car taxes, but even given that, the Cooper D and Polo are cheaper than the Prius.
You are correct, they don't offer the cars in California, but that's only because California doesn't really care anything about clean air. European diesels are not the dirty, polluting cars that their predecessors were, but are some of the cleanest, most efficient cars in the world. Our nut case, backward, socialist, big-brother government is stuck in the 1970's, and refuses to approve the extremely clean
diesel cars Europe is producing these days, because it's more important for California to put on a show
about caring for the environment than actually implementing real
policies to make the air cleaner.
Ultimately, it's not that Prius is all that bad, it just isn't very good, and it's not worth the religious worship that a lot of people give it as "savior of the planet". There are better things out there, but we here in the United States fail to see them because we are blinded by the Prius.