Approximately zero of the indigenous population present prior to settlement by Europeans would have identified as being Australian, or of being born in Australia, or anything like that.

Definitively, yes, Australia "began" with European settlement of the continent.

So what? It’s just a name. Australia was still here; people were living here. Who are you to definitively declare this?

Perhaps this may seem like semantics to someone who doesn’t live here but I find this sentiment at best ignorant and at worst offensive.

Except I do live here, and it's patently ridiculous to say The Commonwealth of Australia is anything but an invention of European settlers. Of which Queen Elizabeth II was the Head of State for 57% of its existence. Which is the context of this comment thread.

It didn’t say “The Commonwealth it Australia’s existence” it said 57% of Australia’s history which I maintain is fundamentally incorrect.

However, I think there is nothing further to be gained here as we would be arguing semantics.

Common sense would dictate that GP is talking about the country not the continent, as continents typically do not have heads of state :)

While that is true, it's not typically how the phrase "Australia's history" is interpreted.

It's common for "Australia's history" to refer to pre-colonisation in addition to the last couple of hundred years.

This is almost certainly because Australians see the country and the continent as 'the same' for all intents and purposes.

The poster wasn't even referring to the last couple of 100 years, only the last 121!

What the indigenous population identify as is irrelevant; in the present day we call that continent Australia.

A state cannot exist without citizens that identify as belonging to said state...

Can't the term "Australia" just refer to the place on the globe? Like if someone was telling me what Antarctica looked like 50,000 years ago, I wouldn't tell them that Antarctica didn't exist back then. I'd know what they meant.

"Australia's history" was a poor choice of phrase exactly because of that ambiguity. In fact it was explicitly referring to the period since 1901, which very few people would consider to be the start of "Australia's history".