I've decided with all those questions where I invested a great deal of time and thought to answer the question, I'll not only save a copy in case the asker deletes it but try to do a take on it. I used to get so irritated if I spent so much time answering a question only for it to be instantly deleted and not even be able to recover my work. Maybe this will help keep me from getting cranky when it happens.
So here's one for a start. The original question asked why US citizens do not favor complete gun prohibition.
US citizens, what major problems do you foresee if all guns/firearms are totally banned, when many other countries seem to be fine without them?
We live a very limited lifespan and experience in ways that I think make it difficult many of us to conceive of our governments becoming completely tyrannical in our lifetimes, or for our economies to completely collapse to one of lawlessness and desperation, or to experience natural disasters which have a similar effect. It seems more instinctive to trust the government when things are going reasonably well.
The framers of the US constitution did not live this type of modern and luxurious experience. Instead, they tried everything they could to limit the government's powers to empower individual citizens. Instead of focusing the bulk of their efforts regulating citizens, they focused on regulating the government. Yet in spite of their best efforts, individual liberties are gradually being usurped every day faster than they are being restored.
This is a matter of values at the end of the day. You may not agree with them and might find them impractical in the age of drones and missiles. You'll have many practical points for sure. Yet it's a deeply important value to red-blooded Americans. It is with a capable weapon in hand that they give themselves whatever fighting chance they can to protect their own freedoms in the worst-case scenarios.
Putting aside these deep-rooted values, a firearm is just a tool. Here in Japan (I am a dual-citizen to both Japan and the US), firearms are extremely restricted to the point of almost being forbidden. They've done a good job with firearm interdiction (along with narcotics) given that the geography of the country is self-contained in an island. Yet there are grenade attacks by Yakuza lobbing grenades into bars, sarin attacks by terrorists in subways, psychopaths mowing people down with large vehicles, and things of this sort. These are rare occurrences but I would attribute that more to the culture and values which promote cooperation (including with the police), the self-contained geography which helps underground economies from becoming too large and powerful (the US has ~1.5 million gang members in circulation, and a great chunk of their profits come from arms and drug trafficking), etc. I would not be so afraid of arming Japanese with firearms. I suspect it'd just make cases like the Akihabara psychotic killer turn into a shooting spree massacre rather than a lunatic mowing people down left and right with a vehicle.
We are also in a complex technological era. We're approaching a stage where 3D printing is going to become widespread, and that includes the ability to print firearms given only a spec that anyone can download from the internet. Even if governments regulate the internet heavily, they've done a poor job with the darknet. Nail bombs are easy to create in your own home for anyone interested and are a source of some very gruesome terrorist attacks that claim the lives of more innocent bystanders than a firearm. We are moving further and further in this direction where we don't need a firearm manufacturer to provide us the most devastating and lethal weapons. If we obsess so much on the tools used for homicide, we may be focusing too much on symptoms over root causes.
I have been to places like Texas and I trust the people there who have large gun racks. They are of sound mind. The person I don't trust is a complete lunatic and psychopath regardless of what weapon he chooses to use to kill people. I'm not a huge gun person but if such a person were to go rampage in my vicinity, my best chance of survival might rely heavily on those good citizens who arm themselves.