This is an argument I see all the time used by the left. It's been promoted by annoying broadcasters like John Oliver and other so-called comedy shows. I honestly think it's bullshit due to a few factors.
For context, I'm not American, but I respect the culture and I'm interested in it.
1. Australia is tough on immigration and border security.
In order for gun control to be effective, you need to have good border security for it work. This is the main reason why gun control doesn't work in Chicago. Not because of the laws of themselves, but because of external factors like anyone being able to drive into Chicago from another state unimpeded. If Illinois had a border with checkpoints, gun control would be much more effective in Chicago then it is now.
Australia has really tough border security. This to the point where they have overseas detention camps where they keep refugees and asylum seekers. This results in all ships being monitored, and seized which makes smuggling shit into the country really hard.
America, on the other hand, has large patches of open borders on the Mexican border that cartels and illegal immigrants take advantage of. If guns are outlawed in America, criminals will simply go to Mexico (or the criminals come here) to get their guns.
2. Australia doesn't border Mexico.
This is expanding more on the point above, but the reason why gun control in Australia is so effective is because they don't directly border countries run by criminals.
3. Gun control only enriches criminals, while law-abiding citizens suffer.
If gun control were to be enacted in America, then cartels and other criminals would be enriched in the process. With weed, we've seen that cartels can make a killing off it. If you make guns illegal, you allow cartels to control the price of it. They would be able to make thousands off a single gun. Would you rather $200 be spent on a gun, which goes to helping tax paying citizens stay employed and help American businesses, or would you prefer that guns go up to $10,000 and allowing cartels to get a new source of revenue?
4. Don't sacrifice your rights for security.
Since 2001, we've had the NSA mass surveillance programme which is in direct contradiction of the fourth amendment. They're illegally spying on American citizens in the name of security. Since then, we've seen terrorist attacks in America which have killed tonnes of people. You now have neither rights, or security.
Those who sacrifice liberties for security shall have neither.
5. Guns don't have to be used to be effective.
I've seen YouTube videos where guns have been used as a deterrent to violence. Yes, it's possible for guns to be used without killing people.
Just watch these videos:
Notice how the gun is used without killing anyone? Amazing, I know!
6. Gun control doesn't mean there's no guns at all.
Just because there's gun control doesn't mean there's no guns in circulation at all. While this might seem like an argument for gun control, it's definitely not. Gun control doesn't mean that there's no guns at all. Guns here and in Australia (I presume) is possible for farmers and for minors to get. Here in NZ you can get a gun if you use it for "hunting purposes", have somewhere safe to keep your gun but you need to have a license to get it.
I'm not interested in seeing New Zealand (where I live) full of guns, but I don't think America should copy us.