From same link.
It's American. The origin of those who started it isn't relevant so much as miners in the US (also here and elsewhere) at that time were from all over the world. In fact most people living here at that time weren't even born here (the US obviously had earlier colonisation by westerners).
Also, I personally dispute "many thousands of Australian miners" going to the US gold rush. Most of those would not have been Australian, but simply moved from Australia to the US as the gold rush here slowed down but in the US it was picking up.
I live in the heart of gold rush territory in the state of Victoria and I can tell you most miners here in the mid 19th century were
not Australian, they were mostly European and Chinese.
Hell, we weren't even a federal country before 1901 anyway we were simply a bunch of separate British colonies