It should be acknowledged that Australians have a special and easy way for coming to US and getting permanent residency. For example, if an Australian wanted to start a business in US, you are automatically qualified to apply for residency right away.
(My information is based on what an Australian couple told me 5 years ago in the US).
True, Aussies now have the E3 visa which is a work sponsored visa just for Aussies. But I came here years before that happened. I had to convince someone to give me one of the very rare H1B visas just to come over to be with my then girlfriend. We eventually got married and I applied for the greencard.
I'm not sure about auto qualification if you want to start a business. I think you need something like $1M in the bank to prove that you have the resources to start...
