A northern or “General American” accent is considered the standard in the US, so it’s kind of hard to make it more so. But someone from Boston who tried to get rid of that Bostonian accent can probably revert to Bahston “why’d you pahk yah cah so fah from the bah” mode pretty readily.
I used to know a lady from Brooklyn, NY and she would pronounce “New York” as “New Yahk” or “New Yawk.” Her funniest pronunciation was “because” which came out sounding to my ears like “be-kwuz.”
