> It goes without saying the Queen (Monarch)is not elected and Queen’s heirs will succeed the Queen’s powers

The Queen has basically zero powers in practice. Her role is purely symbolic, with no practical relevance. Her symbolic existence, whether it be good symbolism or bad symbolism, does not change the fact that Australia already has, in every practical sense of the word, "a form of government where the people are represented by elected officials/representatives". You can even say that her rule over Australia is democratically legitimate due to the failure of the 1999 referendum to remove her.

All the Queen's actual powers in Australia are exercised by her representative the Governor-General. She does not instruct the Governor-General what to do. Outside of exceptional circumstances, the GG does what the PM advises the GG to do. In exceptional circumstances (such as the 1975 constitutional crisis), the GG makes up their own mind what to do – they may inform the Queen of their decisions as a courtesy, but ultimately the discretion is theirs not hers. All the Queen does is appoint and dismiss the GG, and the Queen has always (in recent decades certainly) done so according to the advice of the Australian PM.

If the Queen is physically present in Australia, she can personally exercise her powers rather than going through the GG, but even there she is bound by the convention that she does whatever the PM and ministers advise her to do. In the utterly unlikely event that a constitutional crisis happened to coincide with a royal visit, she might be called upon to exercise some discretion, but I think in such a scenario she would quickly depart from the country so the GG could sort it out.

The only hypothetical scenario in which the Queen might have some real power would be if the GG and PM were engaged in a race to be the first one to sack the other – if the PM instructs her to sack the GG, and she knew the GG was about to sack the PM, she would have a choice whether to follow the PM's instructions immediately, or to delay doing so until the GG had the chance to sack the PM first. That situation has never actually happened (although in the 1975 crisis came close to that hypothetical without actually reaching it.)

She has some other extremely trivial powers – for example, when she comes to Australia, she doesn't have to produce a passport (indeed she doesn't have one) – which again, is primarily a symbolic thing. Anyway, at the age of 94, she has made clear she does not plan to ever come to Australia again, so whatever powers she has when physically in Australia are now exceptionally theoretical. We will have to wait and see who is her successor (most likely Princes Charles, although it is not impossible he could predecease her), when that is (her mother lived to 101, she will be 101 in 2027, but it is not impossible she might even live longer than her mother did), and whether that successor ever comes to Australia as King – it could happen that her death is followed by an Australian Republic, and Charles III or William V, King of Australia, might not make it here before one is instated.

> The US isn’t a “representative democracy” it is a Constitutional Republic

I'm sorry but the US government doesn't agree with you. To quote the educational materials the US Citizenship and Immigration Services provides to prospective US citizens: "The United States is a representative democracy." [0]

And the United States Congress doesn't agree with you either – to quote H. Con. Res 139 of 2003 (passed unanimously), the US constitution "established the United States as a federal union of States, a representative democracy within a republic." [1]

So, I think I will trust the US government and US Congress' position, not yours.

[0] https://www.uscis.gov/sites/default/files/document/lesson-pl...

[1] https://www.govinfo.gov/content/pkg/CDOC-108hdoc94/pdf/CDOC-... see page 8 of PDF