USNA doesn't produce challenges it provides them. Academic and Physical challenges aren't that difficult, nor is ProKnow - the real challenge is learning how to manage time well and learning how to cope with the stress of all the different areas at the same time.
IMHO - the most difficult challenge is getting the appointment. Once you are there - virtually no one is looking to run you off.
^^ IF that is the question, I agree. However, what exactly the OP is asking isn't clear and could be interpreted various ways. Perhaps if he/she would return with a clarification, we could be more helpful.