Because including Australia really ruined ESC right?
It's just crazy to me fans want countries who barely have an interest, like Ireland, to take part while there are also European countries like Slovakia and Hungary who has said no. But God forbid a country who actually has an interest and a passion takes part?
Also Israel isn't European and they've taken part for ages now. For some reason the anti-Australia fans never have anything against Israel's participation, but let's not do that discussion as it's been done to death.
Ruined perhaps not, but it made it stranger and especially EBU's blatant lies from the get-go about a "one-off thing" and all that and the juries push for the country the first years.
I also think we overestimate the "passion" Australia has in this (that's clearly EBU propaganda), because when we look at viewership in Australia, it's actually not that great and my understanding talking with people there, majority of Australians don't care or even know about this contest. It is mostly targeting some parts of the European diaspora and gay community, and that's fine, but it's a rather limited audience.
We obviously can't force European countries to take part, but the ambition to collect Europe under one roof should be there and it's the very concept, it's not a concept where USA suddenly should take part and I still don't get why? It's not about not liking American music or USA as a country (I happen to like both) but rather about the Eurovision concept and to give a forum for European artists and songwriters, we really don't need USA in everything.
I often see the Israel comparison with Australia, well firstly one can take a look at the world map to see that the comparison fails, Australia is as far as possible from Europe and that Broadcasting Union Area (that EBU falsely claims is a criteria to enter Eurovision), Israel is not (it is also within that area). Israel has been taken part all the way since the 70's, and due to geographical (yes it's practically neighboring Europe by just a little water, hardly a full continent and ocean between), political, cultural and social reasons, Israel is already taken part as Europe in various major international events such as European sport championships (like UEFA Euro Cup for instance). Now I won't get way too deep into why Israel is counted as part of Europe in many international events, but yeah there are many factors for that that neither Australia or USA can claim.
I do agree though that the discussion is already overdue, but now it wasn't really so much about Australia or Israel but rather a response to those that also want to drag USA into this. Also, this argument style "since A already takes part, let's allow B" is imho a sort of failed argumentation, two wrongs doesn't make one right.
Just to wrap this up, I have nothing against either Australia or USA or their people, on contrary I like both, my views are strictly on preserving Eurovision as a concept and to promote European artists and culture, to promote the ideas of our continent coming together, it's a protectionist mindset perhaps, but I think in this world there is space for different unique concepts and Eurovision is one of them.
You end your post with saying it's "unique" but you propose ways to basically take away what makes it unique so I am not sure 
