Yes, it does seem as if the car list is biased somewhat towards the odd and rare versions of some seemingly uninteresting Japanese cars.
On the other hand, there aren't too many American cars that fit into this game.
Nobody will want to race minivans, SUV's, or pickup trucks ( except Lightning).
Let's see...
Ford = Mustang (2 versions?), Lightning, and SHO
Mercury = Marauder? (I laugh)
Lincoln = yeah, right.
Chrysler = Crossfire SRT-6
Dodge = Neon Club Racer, Neon SRT-4, Viper SRT-10, plus old RT10 and GTS
Plymouth = phased out like Olds
Buick = only old cars for drags -- '87 GNX, '70 GS Stage 1
Cadiilac = CTS-V, XLR (maybe)
Chevy = Camaro (Z and SS), SSR (I laugh), C5 and Z06, C6? (please, please!)
Olds = no longer exists, but classic 442?
Pontiac = GTO, GTP Comp-G (world's fastest front-driver), Vibe? (aka Matrix)
Saturn = Ion RedLine
Hummer = hahahahaha, could be interesting though simply as a reference.
These are just current models.
And then you have the "Japanese" makers that are really American now...
Acura, Infiniti, Lexus, Toyota (Camry, Corrola, etc.), Nissan (Z, Altima?, etc.)
Honda ( Accord, Civic, etc.)...all American-made cars that will be overshadowed by their Japanese counterparts with better performance.
So, I think that I will welcome all those obscure versions of non-American cars since the American automakers don't make strange, obscure versions too often.
I would love too see 10 or so TVR's in the game (what happened to the Cerbera in GT3?), or 18 BMW's, or 6 versions of the old FD RX-7.
Plus, consider that there are many, many older models that deserve to be in this game, and you will see that the American cars are very well represented.
{edit} I forgot some...Saleen, Shelby, Panoz, and Vector?