I am not so sure America would look much different than Australia, statistically, if you took the large metropolitan areas of high black populations out of the equation.
For instance Chicago, Illinois alone in 2013 logged 421 murders with almost all being black on black or black perpetrated crime.
The state of Illinois does not recognized the 2nd Amendment to the US Constitution and in Chicago fire arms are strictly prohibited.
In Detroit, Michigan there were 386 murders in 2012. Again, the far majority being black on black or black perpetrated crime.
New York City recorded 417 murders in 2012.
There are many other large cities that these statistic will be the same. Philadelphia, Atlanta, LA and many others.
Again, if you removed the large black populated metropolitan areas from the equation, which would include literally 1000's of murders, then statistically the US would not look any where close to the stats you see now.
This black on black crime epidemic in this Country does not reflect the reality of gun ownership in America.
If guns were banned these people would still be shooting each other. Chicago is a classic example.
So, in reality .... banning guns in America means taking guns away from law abiding citizens leaving the criminal and thugs just as armed and arguably more dangerous than before.