It depends on what state you're in, to be honest. Generally speaking, in the midwest, yes; in the north east and south west, not so much and the laws of self defence are more like those of England and other more moderate commonwealth founded countries. As an example, although they are scrotes, does someone entering your front yard to nick your fountain while you are upstairs and that person is posing no threat to you deserve to be shot and possibly killed? You may think so, and that is fair enough - we have our values and there is nothing to say my values are superior to yours..
But what if that person had an hionest and reasonable belief that the fountain was nicked from their front yard and all they thought they were doing was, rightly or wrongly, claiming back what was theirs? Yeah, what they were doing was still wrong, but what if it was theirs and you had nicked it?
If you are under direct threat, the laws in at least NSW and England (and I presume every state in Australia) determine if the level of self defence was excessive based on what you, not the average person, perceived the threat to be. Once the threat was (or ought to have been) perceived by you as passed, you have very little defence. And the action you take to defend yourself that is allowed is very liberal - it has to be manifestly disproportionate to the threat, and even then it remains a partial defence.
This, to me is manifestly reasonable and the US system that allows you to kill anyone entering your land that you perceive may be doing something bad leaves a gaping hole in the law that allows you to kill, say a letter dropper who is chasing a couple of leaflets that escaped thanks to the wind onto your front lawn