I agree completely. Reconsider old policies in light of the new facts. Conclude that nationwide concealed carry is an absolute necessity. Perhaps even conclude that non-gun-owning Americans should be encouraged to take up the practice.
"Reconsider the value of public gun ownership?" Definitely. It's value has gone up substantially since 9/11.
Better yet, return to the early 19th century laws of some states which required all able bodied males in a certain age bracket to own a military type firearm and ammunition, and to practice using that weapon on a regular basis.
I'm not sure where I read that or which states had that kind of law. But I think at least some of those states were the same ones where it's now very difficult for anyone to legally possess a gun of any kind, and practically impossible for an ordinary law abiding citizen to legally carry a concealed weapon.