Australians speak English. They don't speak it like Englishmen, or Scotsmen, or Welshmen, or Irishmen, or Americans, or Canadians, or South Africans - or anybody else who speaks, or claims to speak, English.
They speak their own brand of the language, developed during their years of isolation from other English-speaking peoples. Whom they can understand.
But some other English-speaking people have difficulty in understanding Australians.
And this, to an Australian, is an astonishing thing.
After all, his language is uniform. He has no dialects.
With a few minor variations in idiom and tempo, his language is the same from Cooktown to Perth, whether you travel around the top, or through the centre, or via the southern cities.