The quintessential New York Times Op-ed:
We used to be one nation, undivided, under three networks, three car companies and two brands of toothpaste for all. Today we are the mass niche nation.
In the 1940s and 50s--in addition to Ford (selling Fords, Mercuries, and Lincolns), Chrysler (Plymouth, Dodge, DeSoto, Chrysler and Imperial) and General Motors (Chevrolet, Pontiac, Oldsmobile, Buick, and Cadillac) American manufacturers of passenger vehicles included: Packard, Studebaker, Nash, Hudson, Kaiser, and Willys (Jeep).
Beginning in the 50s several of those cars became part of American Motors. But that hardly limited the niches available to American motorists. At least as early as 1949 they could purchase Volkswagons, Mercedes, Jaguars, MGs and a few other British sportscars.
Throughout 50s and 60s there were also; Volvo, DKW, Renault, Austin Healey, Triumph, Vauxhall, Lotus, Rover, Fiat, Alfa Romeo,Toyota, and Datsun (Nissan) . The 70s saw BMW, Audi, Saab, and several more Japanese manufacturers such as Honda enter the U.S.
Too many toothpastes for you? That was true for Ayn Rand's sister in the 1960s too. As Barbara Branden related the story in her biography, The Passion of Ayn Rand, upon Rand discovering that she had a sister who'd survived World War II in Leningrad, she brought her and her husband to New York to live with her. But it didn't go well, as the sister had no skills to cope with life in a capitalist country.
The straw that broke the camel's back was a trip to a drugstore that overwhelmed the sister with the multiplicity of choices of toothpaste.
In Russia there was only the toothpaste you were given, here there was Colgate, Pepsodent, Ipana, Crest, Arm and Hammer, Macleans. Even though her husband's weak heart needed the attention available only in American hospitals, she returned with him to Leningrad, because she was unable to handle the complexities of shopping in America.
As for the Big Three networks, that was the result of conscious Federal government policy to deny licenses to potential new entrants, not market forces, as Tom Hazlett explained.
[Thanks to Mindles Dreck]