Overall, American TV is still very white. Reading Deadline on a regular basis and noticing the casting choices for pilot season makes that clear. Of course, you can always cherry pick exceptions.
But I'll bet minorities other than blacks are the ones that are really underrepresented, since they don't even benefit from the "token best friend" phenomenon.
EDIT, I googled "racial diversity on TV" just for kicks and found a lot of squawking about it...like this.
Things are looking pretty “token” for lack of a better word.
...with a whopping 46% of shows in the (C) category, it is clear from the data that for most networks, racial diversity often means having just one token minority. Once again, CBS and CW find themselves in the lead in that category with 29% and 19% respectively of their shows.
That's why a show with two major black characters really stood out for me - the usual pattern is to be content with one major nonwhite character.
And NBC being the standout of diversity is a mixed bag because that network is really imploding in the ratings now, while llywhite CBS is still doing the best.