Unfortunately evidence of human settlements by coastal areas degrades rather quickly especially after deglaciation raised the water levels. I suppose early Australoid explorers could have followed the Asian coast
and the Bering land bridge into North America. A direct Trans pacific route seems improbable but cannot be totally ruled out since island hopping was more feasible due to lower ocean levels. The Third possibility is from Africa to Brazil but that is the least likely possibility. Brazil was actually accidentally discovered by India bound Portugese explorers hugging the African coastland and being blown over by storms.
I suppose early Australoid explorers could have followed the Asian coast and the Bering land bridge into North America. A direct Trans pacific route seems improbable but cannot be totally ruled out True enough, but the South African group that eventually populated Australia left plenty of genetic markers and other evidence along the way through India. I'm not aware of anything similar along the other areas you mention.
A bigger problem seems to be that evidence of boat technology simply doesn't seem to exist among the early Australian aborigines. Lots of archaeologists still puzzle over how they crossed open water areas just to reach Australia. Obviously they did it and perhaps a lot more besides. They might have come across the Sahul Shelf when it was exposed during the last glacial period (or even before!)