That Australia is always hot. No, bits of it are hot, but quite a lot of it is temperate and, during winter, the southern bits get pretty damn cold. Not quite Canada/Scandinavia level of winter cold, but not all that far away from it, either. We have fully functional ski resorts in our alpine areas.
That most of Australia is uninhabitable desert. No, we have some pretty large deserts, but most of Australia is inhabited, even if it’s quite sparsely inhabited in places. None of it is “empty” any more than the Mojave desert is empty - people live there and make a living there, there are farms and towns.
That Tasmanian Aborigines were wiped out by the British and are now extinct. No, they’re not; I’ve met some. Their numbers got pretty low, and there was a lot of interbreeding with whites, but their culture survived intact and still exists. I wouldn’t recommend telling one, should you ever happen to meet one, that he’s extinct; they tend to get quite annoyed by people saying that.
That white Australians are the descendants of British convicts. No, only approx 1.5% of living Australians can claim convict descent; there were always plenty of free settlers during the convict era, the gold rushes after 1851 brought ten times more people to this country than convict transportation ever did, and huge waves of post WW2 immigrants increased the population by around a third.
That Australia is full of deadly poisonous creatures. No, we say that to scare credulous Yanks. While it’s true that we *do *have many of the world’s most poisonous creatures, the worst ones are very rare, and you can live your whole life in Australia and never get bitten by anything. Even if, like me, you quite enjoy traipsing around the countryside in reasonably skimpy clothing. I’m 45, have spent my entire life in Australia, and I’ve never been bitten by anything worse than a mosquito. I’ve had people who have never been outside the USA insist that you can DIE from brushing against the wrong trees in Australia. POISONOUS TREES! Er, yes. Right. Whatever.