i've taken a self defense class through my school and of course we learned about the groin strike. In the class we practiced on male volunteers who obviously wore athletic support and a cup. I know it still probably hurt but they were never knocked to the ground or totally immobilized. So if in the real world a person attacked me while wearing a cup one of the most effective strikes would be relatively ineffective. So are there any ways I can strike the cup in a weak spot or if I can "de-cup" my opponent?
You can be very glad that your school offered a self-defense class, and that you took it. Knowing how to spot or deter trouble is definitely helpful, and knowing how to fight if necessary can be life-saving.
The truth is that athletic cups are quite uncomfortable for men to wear. Men know they have to protect that part of their anatomy when engaging in sports or other activities that have a high chance of injury to that area. Teaching self-defense certainly necessitates those cups, but you can bet that those teachers, football players, wrestlers and anyone else who is wearing a cup for a specific activity can hardly wait to get rid of it by taking it off ASAP.
No guy can wear a cup all the time, and in many years of hearing about women's experiences, I have never heard of a man wearing a cup while attacking a woman. Men think their superior size and strength and ability to frighten a woman is all they need to attack her successfully.
So, if you are ever attacked, your attacker won't be wearing a cup, but he might be anticipating a groin strike that he can deflect by turning his legs. Your best response might be to start by hitting him somewhere with your hands (a chin strike, or eyes, or ears) which will distract him for an instant while you follow up with a groin strike with your knee, leg, or foot. A well landed groin strike will certainly take the fight out any man. Yea, Becca!!!!
Have confidence in your training. You have had excellent training, and you can prevail over most of the dangerous situations you are likely to encounter.