Am I screwed?

One grade of a B in an AP course during your senior year will really not have any material impact on college decisions by competitive colleges. For T25 schools that take a holistic view on evaluating applicants, 1 grade out of 25-30 courses you have taken in high school is only 1 data point of much more data points they are looking at. It's fair to say that your academic narrative is much more complicated and will take into account not only your grades but your course rigor, intellectual curiosity/vitality, your test scores, and other factors.

I would focus on making sure your entire application is complete and the best it can be including essays, supplemental essays/answers, recommendations, test scores (SAT/ACT), awards/honors (AP scholar w/distinction, etc), and evidence of intellectual pursuits outside of the classroom and impressive ECs and community service/leadership roles.

If you will be rejected or deferred or waitlisted from NYU and other top Business Schools it will not come down to this 1 grade but other lackluster areas in your application or gaps that have not been fully exploited in your HS career.

Since you have an inherent bias that some/most of the blame for your lackluster grade in AP MicroEcon has to do with your instructor's teaching style not aligning with your needs and expectations, I would recommend that you err on the side of caution before you contemplate using the add'l information section to explain away this grade and others that might not be As. Other students might have been more resourceful than you in organizing study groups, asking for help from someone who has taken College level economics, enrolling in a parallel online course for free on eDx or Coursera, or trying to find other books, videos, and online references to help them fill in the gaps. Assigning blame to your teacher may not gain any empathy from a college admissions reviewer.

Once you arrive on a college campus, you will quickly learn that more often than not, the lecture time doesn't cover all the material you are responsible for and often the onus is on you to figure out what you need to know to get a good grade. Many core classes like Micro or Macro econ are taught by teacher's assistants who are grad students, not professors, so they will not be highly skilled teachers that cater to your learning style and you will need to go to office hours, set up study groups and do your own learning outside of the classroom.

Echoing the other answer, a B in AP Microeconomics will not hurt your chances at getting into top schools for business. If most of your grades are As, a few Bs will not harm your GPA or count as bad academic performance at all - especially if your Bs are in AP classes. You could even get one C on your transcript and still make it into top schools.

This is because college admissions is holistic, so grades are far from the only factor considered for admission. Writing a stellar essay, scoring well on the SAT/ACT, having a solid EC list, having a hook, and getting great teacher recommendations can all make up for grades that are not perfect. Hope this helps!