It's much harder to kill with any other weapon that you could reasonably obtain (vehicle, knife, baseball bat, etc) and that's obvious from what's going on in other civilized countries that don't have a powerful gun lobby.
Is it? It is really tho? Is gasoline hard to get? What about improvised explosives? How hard is it to steal a car or a truck to run lots of people over with? Are you saying setting fire to a populated building wouldn't kill people faster than a gun? Shit there are enough supplies at any local grocery store to build basic IEDs. This premise is bullshit. What is required to kill is INTENT, not a gun.
You know the problem though? You can't defend your home, your family, or your person with gasoline, IEDs, or trucks.
I think it's harder for an average person to build an IED or set fire to a building than it is to pull a trigger.