Here's why:
* Shared Roots: American English and British English share the same origin, Old English.
* Evolution: Over centuries, both varieties have evolved independently, leading to differences in pronunciation, vocabulary, spelling, and grammar.
* Mutual Intelligibility: While differences exist, American and British English speakers can generally understand each other. This is a key characteristic of dialects.
So, while there isn't a separate "American" language, it's accurate to say that American English is a distinct dialect of English with its own unique features.