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