A global attack that destroys everything we've made in seconds.
No grocery stores, no clothes or tools or running water. Suddenly we're back to Genesis but with our human nature unchanged. Would your local community have what it takes to survive?
I think most people would perish pretty quickly to be honest. We've become too reliant on things outside ourselves. Even farmers and rednecks would probably struggle.
No such thing as a "global" emp attack, even a huge sun event will only affect part of the earth.