> Growing up in Australia, every computer I’ve ever owned has defaulted to “US Letter” as the paper size.
I'm not sure how; the UK is an Anglosphere country that uses A4 and desktop machines as far back as I can remember (mid 90s) also correctly defaulted to A4 when printing. I suspect it's more likely to be that there's been English (UK) and English (US) options in OS's for a long time and Aus got defaulted to English (US) rather than English (UK) which carried some settings that weren't correct by default.
> Growing up in Australia, every computer I’ve ever owned has defaulted to “US Letter” as the paper size.
I'm not sure how; the UK is an Anglosphere country that uses A4 and desktop machines as far back as I can remember (mid 90s) also correctly defaulted to A4 when printing. I suspect it's more likely to be that there's been English (UK) and English (US) options in OS's for a long time and Aus got defaulted to English (US) rather than English (UK) which carried some settings that weren't correct by default.