Most Australians have huge bone stuctures and dwarf the much smaller Americans, yes even American bodybuilders. Lee Priest would have been 6'3 and the best bodybuilder in the world if he didn't stunt his growth by starting steroids at age 14.
Nathan Jones is a good example of the size of a normal average Australian male. Here he is standing next to a typical average American, see the difference in the genetics of the Australian, the product of evolution on an isolated island with no natural predators or enemies:

Dude, your first statement is beyond ignorant. Especially for the fact that Anglo Americans and Aussies came from the same place or origin. Then you have the People of mixed African origin over here. Also when the Europeans came over to America they were dwarfs by Native Americans, who were around 6 feet tall. This was due to their high protein diets.
In fact, Asians raised on high protein diets are significantly taller than their predominantly rice eating counterparts, and Asian women with higher protein diets have bigger breasts as well.