Why wasn't slavery more widespread in Australia, like how it was in the American colonies? Why didn't the African slave trade extend over to Australia, giving Australia a large black population?
Australia was settled much later than the US: the first colony wasn't founded until 1788, and large-scale immigration into Australia didn't start until well into the 19th Century, by which time slavery was abolished in the British Empire.
At the time of British settlement in Australia it was not legally possible to be a slave in England, and prior to settlement, Captain Arthur Phillip, on appointment as Governor to the new colony noted in his preparatory memorandum
The laws of this country will of course, be introduced in South Wales, and there is one that I would wish to take place from the moment his Majesty's forces take possession of the country: That there can be no slavery in a free land, and consequently no slaves" .
So it has never been legally possible to own slaves in Australia.