I typically don't capitalize either, but black Americans are an ethnicity, like Italian Americans - a group w/a distinct history, culture, & sense of identity; white Americans (like "people of color") aren't, but are an amalgamation of ethnicities defined only by who they aren't.https://twitter.com/AsteadWesley/status/1274560537523781633 …
My heritage is American and also ethnic (Irish, Scottish, English). What would white add to that?