When you listen to a professional newscaster, you are hearing an “all-purpose” American accent, very similar to how black comedians make fun of white guys. It’s a mode of speaking designed to be understood by a wide variety of ages and backgrounds. It’s also totally alien sounding, especially when they lapse into a Spanish voice for words like “Nicaragua”.
In 1990, I relocated from New Jersey to Georgia. Originally, I had a curt New Jersey accent, like Jim Norton. My first year, I roomed with a guy from Rhode Island, and when I went back to Jersey for vacation, my friends couldn’t believe what a horror show my speaking voice had become. I was the caricature of the braying Yankee.