Everyone speaks a dialect.
Standard English is a dialect, or more precisely, a collection of dialects. Standard American English differs from Standard British English, Standard Australian English, Standard Canadian English and the standard Englishes spoken in India, Nassau, and elsewhere.
Some dialects have more prestige than others, but one dialect is no more “correct” than another. However, in all languages, one dialect rises to the top, so to speak, and becomes the recognized “official” form of the language to be taught in schools and used in government and commerce.
One mark of an educated person is the ability to speak and write a standard dialect in addition to whatever dialect is spoken at home.
A dialect is not the same as an accent.
Standard American English is spoken with various accents.
EXAMPLES of some US Regional Accents
New England as spoken by Katherine Hepburn.
Boston Urban as spoken by Mr. Howell on Gilligan’s Island and Cliff on Cheers
New York City as spoken by Archie Bunker on All in the Family and Fran Drescher on The Nanny.
Upper Midwestern as spoken by the characters in Fargo
Chicago Urban as spoken by John Belushi
Pacific Southwest as spoken by Whoopie Goldberg in her one-woman show.