We first noticed black squirrels when we went camping in British Columbia 3 years ago. There may be some in the U.S. but I've never lived in an area that had them before. The ones I'm used to are gray or reddish brown. Canada has those too, but the black ones outnumber them. At least they do in Toronto.
I remember the day our moving truck arrived a moving guy overheard us marvelling at a black squirrel on the porch and asked, "You've never seen a squirrel before?" He was surprised when we told him that black ones were new to us.
Now? They're no big deal. There everywhere and we cross paths with them several times a day. I think I'm going to miss them when we move.