Here's my opinion. Take it for what it is...

Gun ownership does not and never has been an "only cause" of low crime, tho it can contribute to low crime. Many areas of the world where gun ownership is high there exists high crime and/or gun violence also.

For Americans, gun ownership as a "deterrent to crime" is something of a side street on the main highway laid out by the Constitution.

Gun ownership as laid out in that document is expressed to be a RIGHT. This is not contingent upon its utility as a DETERRENT, tho in some cases it is a deterrent.

Robbing a population of a right may have some short term utility but it is always unjust. In the case of Australia, the robbing of the right may not even appear to have ANY social repercussions because of the lack of crime in the first place, guns neither causing all crime nor stopping all crime. Point being that in a homogenous society with low crime, the mere addition of guns does not necessarily create crime. The other side of the coin is true, too. In high crime areas, removing all guns does not stop crime.

One of the main reasons Australia has such low crime is that it has a very homogenous population, culturally speaking. The Australians having been quite successful at marginalizing and/or effecting genocide on their indigenous populations and diversity of population groups representing competing values is low compared to other nations such as the USA where cultural diversity and resultant competition between highly diverse groups boggles many visitors' and social anthropologists' minds. Such success is also represented in areas of the USA; Wyoming for example.

Having grown up on the East Coast and travelled and/or lived in most of the US States, I wonder why our crime rate isn't higher than it is.

An interesting study will be, say, Norway, where a homogenous population is now being opened to relatively large numbers of foreign immigrants with competing ideals, goals, values. Just watch the crime rate there and in 20 years let's have this chat again...