Ah, word. It's what most US-ians in movies sound like because of hollywood and therefore it's mostly what folks consider "American English". It's not the default though, because there's also western/texas/deep south english which is your typical cowboy to hillbilly range of accents seen in wild west movies, or when coastal libs do that annoying thing here equating all southerners to inbred reactionaries. The Midwestern accent is a bit on the stereotypical Canadian side, at least to me, and the New York/Boston/New England accent is also sharply distinct. AAVE (African American Vernacular) can also differ among regions and is different from how non-Black US-ians talk in many cases.