Midyear report Crisis?

I just finished the first semester. I have held my own pretty well in most of my classes. I received my usual As and Bs. The problem is AP Calculus. I currently have either a C- or a C on my midyear for that class (depending on my Midterm exam which is questionable.) I have been struggling in that class all year and it isn’t any senioritis or anything since all my other grades are on par with the others on my transcript.

I was wondering:
How detrimental the C/C- would be?

If a college already accepted me, is there a high risk of my acceptance being taken away?
How important are Midyears to the following Schools?
-Stony Brook (SUNY)
-Rutgers New Brunswick
-Univ. Maryland College Park
-Northeastern
-Boston College
-Georgetown

Please let me know, any help or advice is appreciated. Thank you!

Most likely your decision(s) will not be rescinded. One C isn’t the end of the world. That being said, if you applied as a math major it probably isn’t the best.