General summary - many American's believe being able to carry guns means:
a) their Consitutional right to bear arms is being upheld (I recognise that some people actually only
want the right rather than to actually carry one around at all times; and
b) carrying a gun makes for a safer society.
I
personally think guns make for a less safe society, but that it is a problem that can't be easily "fixed" in the US. First up, I have dug around and found a publication by the NZ Dept of Justice:
http://www.justice.govt.nz/pubs/reports/2002/intl-comparisons-crime/international-comparisons-of-violent%20crime.pdf
Which basically says (see page 4) that there is a crapload more violent crime in the US.
I have a hard time finding recent info on the degree to which firearms impact this. The best comparative info I have found is:
http://www.cfc-ccaf.gc.ca/en/research/publications/reports/1990-95/reports/siter_rpt.asp#FINDINGS
It is a bit like Sesame St - one of these things is not like the other...