There is a map from André bianco, genovese i think, that shows an island west of africa that is supposed to be brazil, this map is frim 1448, i believe this map is in london, and is the only thing, anthough not solid proof that the portuguese fist discovered america.
Columbus story is a tough story, his sons wiped out all registry, and little to none registry exist about his passage over portugal, but at the time only portugal was capable to make such voyages and sea preparation.
About australia, portugal had alrady colonized timor island centuries before...right now there is one australian scholar with one damaged chart trying to prove it was the portuguese who discovered it.
karghnout, the portuguese colonization process was based one key fortresses for assuring trade flow, and then population.. so what you said is half true.