How will a B in a community college course affect my admissions chances?

I have had a 4.0 GPA (unweighted) up to this point in high school and am currently a senior. I'm planning on majoring in chemical engineering and decided to take differential equations from my local community college. Unfortunately, my professor turned out to be really bad, and since most of the class (75% of my grade) is based on the scores of 3 tests, I am very worried I'll end up with a B since I did not do too well on the first one. I know my EA schools won't see this grade unless I get deferred, but I am worried that many of the other top schools I am applying to RD, such as UPenn, Princeton, and Northwestern, will see this B and treat it as an indication that I cannot handle college-level coursework. I know that traditionally, one B does not make a large impact on admissions, but I feel like it kind of invalidates all the work I put into maintaining a 4.0 GPA so far. Do you think I should explain why I got a B in the additional information section of the common app, and do you think that it will impact my chances at top universities?