I was in California. It was in the 1980s.
Friends who said they were from "Britain" who were being interviewed at the same time were asked where they learnt their English.
Dialects and accents are interesting. I thought the Irish had a big part in development of the generic american accent.
The Australian accent comes from the lower class English accents like the cockney and a bit of Irish. These two groups were most of the convicts that were the first white invadors of Australia
The Irish may have influenced it in some parts of the country; but Germans were an early and strong influence. Have you ever been to Minnesota? The traditional Minnesota accent sounds almost as if the person was a native speaker of one of the Scandinavian languages and learned English as a second language - but it is actually the regional accent of people whose L1 is English. I worked with a man who was a PhD candidate in Chinese who was from Minnesota. It was always strange to hear him switch from English with a Scandinavian accent to Chinese with no Scandinavian overlay. Great guy to take with one to dinner at a restaurant where the management spoke Mandarin.