Here's why:
* Origins: Cary Grant was born in Bristol, England, and his original accent was a standard British English accent.
* Hollywood Influence: He moved to Hollywood in the 1930s, and the film industry at that time often encouraged actors to adopt a more neutral, American-sounding accent. This was partly due to the desire to reach a wider audience and to avoid regional stereotypes.
* Unique Blend: Grant's transatlantic accent was a unique blend of his British roots with a cultivated American intonation and pronunciation. It was smoother and less regional than either standard American or British English.
It's important to note that the transatlantic accent was popular in Hollywood during the Golden Age of Cinema. It was a distinctive feature of many famous actors and actresses of the time.
So, while Cary Grant's accent was ultimately a blend of his origins and the demands of his career, it's often categorized as a transatlantic accent.