The U.S. is also not Australia. If they repeal the 2nd Amendment which is considered inalienable and not to be infringed they still have the problem of enforcing it.
It hasn't been defenders who have guns that have been killing people. Offenders don't care about these laws.
The Defenders in the U.S. will be forced to prove this point if they attempt to take the guns. That won't be pretty.
Some people may be fine with making themselves into easy targets for criminals, and criminals includes government tyranny. Many of us are not so naive. We know criminals don't care about laws, so won't care about gun laws. All it does is remove the ability for people to defend themselves from said criminals.
Will accidents happen?
Yes.
That is called life. People trip, hit their head, and die frequently.
More people are killed by fists in the U.S. each year than guns.
Freedom is dangerous.
It is still preferable to slavery.