It depends on what organisation gets hit in the EU. If Greece defaults you can bet the debt will be like playing musical chairs.
Some other small EU companies have lent money to Greece and they will take a hit as well, so how it affects them and what the ECB does about it all will be a major factor. If they prop these smaller countries up with debt buying (bonds) it might not be so bad but if they don't you may have other smaller countries going bust.
The EU is America's biggest trading partner, bigger than Japan or China I think, so if there is even a ripple in the EU the the ripple will travel to the US Markets. Also a lot of organisations like funds and banks have invested heavily in the Greek and EU markets so if Greece defaults you could well see the Greek markets tanks.
Whatever happens to the US markets will happen to the Australian markets. US banks and financial institutions may well use other markets to hedge their losses, like the ASX. A lot of US financial institutions are in Australia, all the big ones and they wont miss out on hedging losses in the Australian markets you can count on it.
Just my opinion of course and no facts and figures to back this up.
