You might think that Canada, or perhaps Texas, is the closest approximate to the United States. After all, both share borders with our fine republic and both of them have similar accents. But I contend that Australia is our closest cousin.
This makes sense demographically, as Australia and America were both settled by people who got kicked out of England. Specifically, America got the people too boring for England (Puritans) and Australia got the people too exciting for England (nefarious felons).
Puritans were super religious people who wore buckles on their heads and warmed themselves during the winter by huddling around bonfires made out of witches.
Conversely, everyone in Australia claims to be descended from an archetypal plucky bread thief who, despite incarceration, was actually “quite a likable bloke.”
For a long time I thought the whole country was delusional, what with the auspicious lack of evil-doers in the family tree, but now suspect this might be accurate given how easy it was to get hanged in the 18th century. (Basically in 18th century England anything greater than cute crimes, like “bread thievery” or “wanton violence” resulted in immediate death.)
Australians are actually misplaced Southerners. The American state of Georgia was also a British penal colony. However as the American revolution approached a good boil, and the Americans got to dumping crates of tea in harbors and stockpiling muskets, the British decided perhaps it was not such a bright idea to keep funneling angry thieves that direction. So they redirected their penal flow to Australia, clear on the other side of the planet.
This perhaps accounts for some of the political differences between the two peoples. America claims “the Founding Fathers” as our political progenitors, whereas Australian has “the First Fleet.”
Now in the case of Australia, it doesn't make sense to idolize a bunch of colonial felons who got caught pilfering muffins. You never hear parliamentary tiffs conclude when someone says, “Do you know what Scraggy McLeak would do about taxes?” Because Scraggy would steal some bagels and then link up with Irish dissidents.
This is clearly contrasted with the more respectable American Founding Fathers. These were Enlightenment thinkers who believed in liberty and also happened to own a lot of black people and used wooden teeth. There is no way they could have gotten anything wrong, which is why we try and do exactly whatever they said we should, forever.
Our shared ancestry with the Australians coupled with rugged frontier settlement may account for some of the common personality traits enjoyed by either nation. Both groups find it perfectly acceptable to kick open a door, grin, yell “I'm new here and we're all friends/mates now!” and then guzzle a beer right there in the doorway. English people can't do this sort of thing as it's against the law to make direct eye contact with strangers anywhere south of Birmingham. Canadians literally cannot speak above 12 decibels of volume, except when beating the hell out of each other with hockey sticks. This sort of gregarious gusto is unique in the Anglosphere to America and Australia.
Indeed, the similarities between Australia and America are striking. May they exist in friendship forever more! (Unless we feel like invading Australia for its abundant mineral resources.)