So, there was an Alternative History Hub video on "What if Mu was real?"

This was not too terrible overall, but the ending was severely disappointing. Apparently he couldn't imagine Europeans simply not being able to colonize something despite things being very different.

So, how does this work? Well, the map is a composite of different wikipedia maps for world currents and plate tectonics. I suspect that the western part of Australia (hereafter Pacifica) would probably be more mountainous, but I'm actually not sure. To be honest, by plunking that continent and some islands in the Pacific Ocean would probably cause a lot more climate differences than here. For sake of my sanity I tried to pretend nothing much would alter.

Anyway, I'm hoping to come up with more for the history of this particular Earth. I'll update here as I go.

6/21
Australia was first inhabited at around the same time as in our timeline, between 65,000 and 50,000 years ago.
Because of the Ice Ace, a land bridge formed between Australia and near-by islands. It expanded to the east far enough to nearly connect with North America, allowing for humans to migrate by land and sea between 30,000 to 15,000 years ago.

Even after the Ice Age ended, sea trade flourished across the region due to the proximity of the islands and continents, though once climate changed caused southern Australia to get drier, most people kept to the wetter northern coast.

Trade in spices flourished as early as 2000 BCE.

As early as 697, the Tang Dynasty began sending exploratory vessels to the south and east to see if they could expand the empire in that direction. While no colonies were established to the immediate south-east, an attempt was made to colonize Australia, but it ended up becoming an established trading post. Further explorations eventually saw the western coast of North America where some trade and a colony was attempted around 900, but this colony ultimately failed after the fall of the Tang Dynasty in 907.

Maps of the area of the legendary lost colony began intriguing Chinese scholars and during the Ming Dynasty, so Zheng He lead Chinese ships explore to the far east and, in 1430, reach the western shores of North America, which they call Penglai. The goods he returned with encouraged continued trade in that direction, though it did not help the fleet and the various voyages by it ended in 1433 after one last trip to the coast of the Americas.

Because of the trade, horses, pigs, chickens, and similar animals began arriving in the Americas and Australia and kept arriving as the trade network continued. Diseases also spread along the line, so that by the time Columbus arrived in 1492 the greater population of the Americas and Australia had been exposed and developed methods to deal with the diseases. New weapons had also spread.

The Qing dynasty began an eastern expansion over various islands as well as the northern part of Australia and western coast of North America. Though they had some early successes, they were ultimately driven out by Indigenous people as well as the British Empire.

Though several attempts were made to colonize Australia and the Americas, with the weapons, animals, and resistance to disease, most were thwarted early on, though that didn't stop European nations from claiming the various lands anyway and causing a lot of issues. As pressures continued, various Indigenous tribes and nations united to repel the invaders.