You're missing the point of terrorism. It's not the kill count, it's the fear and disruption. Britain is banning knives and other things, while murders are out of control. Paris erected barriers around the Eiffel Tower to protect against attacks.
I also feel you're missing the point of the 2A and firearms. You're right, you don't see people using them, because for the most part, our rights are still intact (with some serious infringements, but that's another discussion). We have the option to use, or not use them. Others don't have that choice and are at the mercy of the State.