Replying to U.S.A Gun Laws?

Would love to hear from anyone from the US why there is such a huge resistance to changing gun laws. I understand its in the constitution but cant the constitution be amended ? Protection doesn't really make sense in my head either because if no one had guns then do you need a gun to protect yourself?

I'm just trying to understand stances here because im not from the US and therefore not the deepest knowledge on this. To me its super interesting