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.

Even if removing guns is not feasible there are some tools that could be effective, such as required liability insurance. Wouldn't impact responsible gun owners whose premiums would be near zero, but could make it too expensive for nutjobs to own assault rifles. Might also help with other issues like straw purchases.

But even mild measures like that are unlikely for at least the next 10 years. It's unimaginable that any discussion on the topic would be possible in the current post-factual political climate.