Goldfields, I think they're different copperheads.
This is what ours looks like: http://www.marietta.edu/~biol/biomes...heads_5968.jpg
When I searched Australian Copperhead another snake came up, and it didn't appear to be a pit viper.
Notice the triangular head and holes in front of the eyes (the pits), in the U.S. version. They are a pit viper like all but one of our venomous snakes (The Coral Snake)
Coral snakes look very similar to a native scarlet king snake
and milk snake
, which are non venomous and more common.
Pit vipers also have slanted eyes. The eyes in the first pic were apparently dilated for some reason or another. http://www.hiltonpond.org/images/Copperhead02.jpg