But you are already in a situation where there is massive illegal gun ownership amongst criminals. Banning legal gun ownership in the US probably wouldn't even make a dent on that. Considering that fact then the self defence argument isn't idiotic because you are not going to be able to easily reduce the illegal gun ownership.
I never said it could be done overnight, it requires a culture change.
Besides, many (or most if I recall correctly) of the mass US killings are done with
legally owned weapons, to obtain a gun illegally firstly rules out prior ownership (that negates much of the 'crimes of passion', it also doesn't make obtaining weapons easy for people with severe mental problems (not likely to have criminal connections, people willing to provide them arms over-night).
Many crimes will continue of course, much of the gang related crime & crimes related to criminal behaviour (theft/robbery) - but you will see a significant reduction in accidental gun deaths, crimes of passion, high school shootouts or mentally ill people going postal.
By forcing a person to break another law to obtain a weapon you also increase the chances of that person getting caught.
Considering the success of armed insurgencies around the world (including against the US military) I don't think this is as black and white as you seem to be painting it.
You must have an interesting & unique definition of success.
You seem to be ignoring the size/power of the US military compared to that of other nations with insurgence (who are usually aided by external parties anyway) - which in the case of a domestic US civil war would not be probable (due to the nuclear deterrent).
^wow, is that last paragraph seriously a justification?
That along with the fact that historically a police force didn't exist across much of the US is the reason for the constitutional right to bear arms.