Things I still don't get about Australia - No. 16

Why do Aussies sometimes talk like Americans? Pasta is pronounced Parsta, project is prohject and yoghurt is yohgurt. I don't care in the slightest but for a country that has often kept much from it's British roots, some of which the UK itself has begun to abandon, hearing American pronunciation seems a little strange. Or is it a linguistic version of convergent evolution? Odd.