The US, especially east of the Mississippi River, has considerable diversity in regional dialects as well, well beyond the New York vs. Southern vs. Midwest which was mentioned previously in this thread.
An Alabama “Southern accent” is different than a typical Georgia accent (the “drawl” is much more apparent), and South Carolina, Tidewater VA, etc. are also distinct from each other. Rural southern Appalachian (y’all becomes you’uns) accents are very different from other “Southern” accents, and can be difficult for outsiders to understand. Baltimore residents have a distinct dialect (Bawlmerese, hon!), which is similar to Philadelphia (their NFL team is properly known as the Iggles). In Boston (Bahstin), you pahk yaw cah neah da Dunkin Donuts to get a drink at the bubbly.