In particular, read the Notes section next to the US. Our immigration rate, if you counted it the same way, is about the same as Australia. But comparing US immigration to Australia immigration is apples to oranges. Australia has quite strict regulations on who it accepts as immigrants, and doesn't even accept a single refugee. Meanwhile the US has an illegal immigration population that dwarfs the legal one, we basically don't have a Southern border.
"Australia’s humanitarian refugee intake will be set at 18,750 people per year, making it the third largest humanitarian programme in the world."
https://www.businessinsider.com.au/australias-refugee-intake...
I assume you came to this misunderstanding because of our (legally and morally dubious) policy of not settling refugees that arrive by boat. I assure you we do accept refugees.
Other posters have dealt with your other factual misconceptions than I can, but a personal appeal from me to resist posting with a sense of authority on a topic you apparently are so unqualified to make statements about.
Perhaps it would be more accurate to say you didn't have a southern border. From 2005 net immigration from Mexico has been negative:
http://www.pewhispanic.org/2015/11/19/more-mexicans-leaving-...
Lets not forget that all Australians except for Aboriginal people are technically immigrants.
The debate will never cease.
In the thousands of years Aboriginal people had here, it's a pity they didn't unite in greater numbers, and have the foresight to build a few permanent structures as symbols of a united people, both for their own reasons and in anticipation of invaders from across the seas.
Upon seeing obvious signs of a united people, impressions would have been different. But they didn't have a sense of ownership of the land. It never occurred to them that other humans may come and want what they had. They were unprepared.
It puzzles me why they couldn't envision such an invasion, when they would invade each others tribes routinely. They were not strangers to war and conflict including turf wars over hunting grounds. But they failed to unite as one people, probably due to the huge distances in Australia, but still... 40,000 years was plenty of time to get organised.
By your standards even the Aborigines are immigrants, having arrived some 60000 years ago.
I'm pretty sure Australia has a higher immigration rate than the U.S (a quick google supports this) and our net immigration rate is papering over some of the structural issues in our economy in turn helping us avoid a recession.