Here's why:
* Popularity in the US: The American Shorthair is the most popular breed in the United States according to the Cat Fanciers' Association (CFA).
* Wide Distribution: American Shorthairs are found all over the world, thanks to their history as working cats on ships.
* High Number of Unregistered Cats: Many cats, particularly those from mixed backgrounds, are not registered with any breed organization. This makes it difficult to track their numbers accurately.
Therefore, while the American Shorthair is a strong contender for the most common breed, it's important to remember that there is no definitive answer due to the vast number of unregistered cats worldwide.