Matters become more complicated when models within brands are considered. Sometimes model names and what they represent can remain stable for many years. For example, Buick's Roadmaster model was at the top of the Buick line 1946-1958, the Super was the middle Buick 1940-58 and the Special what the low-priced line 1936-58. The Century model, a sort of hot rod on a Special chassis with a high-horsepower motor flitted in and out of this progression. For 1959, Buick renamed all its models, which must have created a good deal of confusion for prospective buyers.
Then there are model names that drift downward. For instance, in 1953 the top of the Chevrolet line was the Bel Air, but in 1959 the name was used for mid-range Chevys, the top model now being called the Impala. Finally, in the American industry there are model names that appear for only a few years and are then discarded.
When Japanese car makers entered the American market they sometimes kept model names for decades. Toyota at first simply marketed various models under its brand name, these models (think Camry, Corolla) in some ways being analogous to corporate brands such as General Motors' Pontiac, Oldsmobile and Buick. Aside from its separate Lexus luxury brand and the entry-level Scion introduced years later, Toyota sells a variety of models including Yaris and Avalon in additions to those just cited. Theoretically GM could have marketed its cars as "GM Chevrolet," "GM Oldsmobile" and so forth essential tracking "Toyota RAV4," "Toyota Prius," etc. So in many cases, it can indeed be useful to think of Japanese models as brands.
Consider the Honda Civic. It first appeared in the USA in 1973 as a small car well suited for urban driving. By the 1980s, small Honda Civics were still being sold, but larger four-door sedan and station wagon versions had appeared. Later, Civics were offered as coupés and sedans, and these were larger than before. Growth continues to this day, Civic sedans being a notch smaller than standard, mid-size cars such as the Honda Accord, Toyota Camry and Nissan Altima in the American market.
Honda could have retained the Civic name for its smallest car line, but instead used it for an increasingly large automobile. Why? An automobile historian might be able to find documentation or witnesses to the process, but I'm just a blogger who can only offer a guess. I suspect that the market for really small cars in the USA has never been large, so Honda felt that the Civic brand name had value and could best be retained on vehicles that were smaller than average, though not small in absolute terms.
This is the Civic in its initial form.
A recent Civic.
Honda still found that smaller cars had their place in America, so Fits appeared here starting in 2008.