It's also applied to switching dialect, word choice, and even accent. Lots of people in the US who grow up with any kind of regional or ethnic accent or English

It's also applied to switching dialect, word choice, and even accent. Lots of people in the US who grow up with any kind of regional or ethnic accent or English-variant end up being capable of code-switching to Standard American English, especially if they move around much and/or attend school somewhere outside the area where their dialect is normal, though even regional schools will provide some social pressure to avoid non-standard accents or dialects that are common in their areas. AAVE (African-American Vernacular English) is a commonly-cited variant from which one may wish (or feel strong pressure) to code-switch to SAE, but similar (if less race-fraught, so perhaps not directly comparable) pressure exists for people with strong Bostonian or Appalachian or rural-midwestern accents, or most anything other than SAE. The positive reason for this, is that it allows potentially extreme variants and dialects to co-exist while letting everyone still communicate clearly with others (by code-switching to whatever's considered standard). The down-side is that it often exists alongside negative stereotypes about those who can't, or choose not to, code-switch to SAE (but, of course, refusing to becomes its own counter-signal for very high status—Fussell, for instance, observes that adhering to SAE is a middle-class and up tendency, but not among "old money" or his "top-out-of-sight" rich, since they don't need, at any point in their life, to give a damn whether some employer or other gate-keeper judges them worthy or intelligent or whatever).