I want to assure you that I’m not trying to be charitable or trying to placate you. Your academic record is well in line for admissions to CMU. There are many kids who are accepted to selective colleges with stats well below the averages because they have some special tag on their app whether it be Development, Athlete, Legacy, URM, Celebrity or anything that a college decided they want to have in their community. You are not in that number though your URM status would have made you possibly so eligible.
That is not to say, however, that you should not be concerned about the rigor of the program. IMO, in certain majors you find a larger number of kids who live and breathe the subject matter. Some of those kids may not even have the academic profile that you have in that they may be crazy genius in the field and lacking in other concerns. It’s tough when you are in a field that has a critical core of those types. CS in one of those fields that tends to get such students