"Paul J. Adam" wrote:

[ boiled down to a single point...]

[...] it's a fair assumption that any casual burglar or
opportunistic mugger might be carrying a firearm.

That's true anywhere; criminals obtain their firearms illegally,
after all. The big difference is that in the US, the intended
victim is much more likely to possess a firearm - and thus,
could be lethal to the criminal. Combine that with the usual
escalation of punishment when a crime involves the use or threat
of a lethal weapon (not just guns) - and we have the amazing fact:
Wherever a US state has enacted a liberal policy for issuance of
handgun permits, crime has decreased. Criminals are cowards;
they will invariably choose a weaker target for their crimes
- and avoid locales where their victims may be in a position of
greater strength to ward off an attack.