FORTUNE -- When the 2011 model year came to a close at the end of September, the Detroit Three had much to congratulate itself for.
Competing against their Japanese rivals (admittedly handicapped by an earthquake and tsunami), they made some nice gains. General Motors (GM, Fortune 500) and Chrysler notched some improvements in market share, Chrysler climbed back into fourth place in U.S. sales ahead of Honda, and the Chevrolet Cruze emerged as a top-seller in the hotly contested compact segment.
One significant set of important customers , however, continues to elude the domestics and those are the ones on the East and West coasts. Despite years of trying, GM, Ford (F, Fortune 500), and Chrysler remain laggards in these markets, which are critical not only because of their size but also because of their influence.
"Trends start on the coasts and in bigger city centers and filter themselves inland to the conservative Midwest," says Edmunds.com senior analyst Jessica Caldwell. "With a few exceptions like the Chrysler 300, the domestic automakers haven't been particularly trendy in the recent past, but that's changing a bit."
Of the top ten-selling vehicles in California, eight are Asian and one is European. The only American nameplate in the top decile is the Ford F-150 pickup, a vehicle that ranks first in the country as a whole. (The sales figures were compiled and analyzed for Fortune by Edmunds.com, using data from R.L. Polk)
It is a similar story of import domination in New York State. Here, eight of the top-ten sellers are Asian, and only two are domestic: the Chevy Silverado pickup and the Cruze.
Contrast that with domestic sales in a Middle America market like Illinois. There, GM has five of the ten best-sellers and Ford another two. In Texas, six of the top ten are domestics.
Overall, 59% of the cars sold in California are Asian and 18% are European. In New York, 54% are Asian and 12% are European. Illinois, by contrast, splits only 45% Asian and 9% European.
There are several reasons for these differences, some historical and some cultural. Geographic proximity makes international influences strongest on the coasts. As the centers of the entertainment and media businesses respectively, California and New York are more closely attuned to developments overseas. And it doesn't hurt that the domestic sales offices of the Asian automakers are largely located in Southern California, while European importers are mostly clustered near New York City.
A decade ago, you could have ascribed these regional differences to variances in population density, driving conditions, usage patterns, and gasoline prices. Detroit made big cars, traditional sport utilities, and pickups, while importers prospered in mid-size and smaller car segments and crossover SUVs. Each served a more or less discrete universe of users.
But Toyota (TM) and Nissan have now joined the Detroit Three as full-line producers, and the battlegrounds have become concentrated. White space is gone. The same four product segments top the sales charts in all of the three sample states. Sport utilities rank tops in New York and Illinois and second in California, where the basic economy segment is king. Mini sport-utility is the fourth leading category in all three states.
That suggests it is no longer sufficient for GM, Ford, and Chrysler to stick with their traditional areas of expertise. They must learn how to compete across the board in all segments, a lesson they are belatedly coming to understand. "The Chevy Cruze and Ford Fiesta are selling well in California now, but the import mindset there won't change overnight," says Caldwell. "The coasts are home to the biggest markets in the country, so domestic automakers have to have a solid foothold there."
Despite the presence of so many strong players, some regional differences seem immutably set in stone, a product of strong dealer networks, usage patterns, tradition, and lifestyle.
California customers have a sharp eye for premium luxury. In the state where the valet parking stand ranks as a major social gathering spot, Mercedes is the seventh best-selling brand and BMW the eighth. In the latest month, Californians also anted up for 180 Ferraris, 167 Bentleys, and 111 Rolls-Royces. That dwarfed even New York, which accounted for only 75 Bentleys, 71 Ferraris, and 22 Rolls.
Illinois remains GM country. The Chevy Equinox ranks first in sales there, the Cruze third, Silverado fifth, and Malibu tenth. New Yorkers show an unusual preference for Nissan, which is the fourth leading brand. While Nissan trails Ford, Chrysler, and Hyundai-Kia nationally, it leads them in New York.
And Texas remains, defiantly, the home of the cowboy's Cadillac: the full-size domestic pickup. Ford, Chevy, and Ram hold down the first three spots in sales, and the F-150 outsells the most popular passenger car, the Toyota Camry, better than three to one. As for the heavily touted Toyota Tundra, which is built at a plant in San Antonio -- it doesn't even crack the top ten. 
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