The answer is actually simple. OUR today’s ENGLISH is derived from people who spoke English, German, French, Italian, Yiddish, Polish, Chinese, Spanish and most of the other languages of the world. The children of those immigrants, got put into schools, learned English and also saw that that IRISH girl in the next row was kind of cute, and she thought the ITALIAN guy was pretty neat.
The getting together of those children is the thing that is today called the American “Melting Pot.” Words from all the European countries became a normal part of OUR language.
Makes sense since all Oz immigrants were from the UK so they kept some of the accent. I’m sure other UK colonies contributed people to Oz which change it some but not all. Then there’s NZ.