I can't speak to Australia, but I've seen little evidence of any significant benefit to be gained by the type of border measures implemented by the American Right. There is significant value in improving our points of entry, because this is where the majority of contraband crosses the border, but the right doesn't really focus on this issue.
If you stop people... You also tend to stop the trafficking of other illegal items/substances.
Every nation needs secure borders... It is about being safe for the countries citizens at the end of the day.
Actually it really does not work that way. Yes, you stop the people that just walk over but criminal organization have no problems getting into the US, they never have because as long as the system is controlled by people, money will make a way.