The quick answer is "no." You may have to show where the money came from - but as long as it is a legitimate "inheritance" and all the appropriate taxes were paid on that in Australia, you should be ok.

The transfer of that much money will be declared by the bank to the US Treasury Dept. - both the bank in Australia that is making the transfer and your US bank receiving it. You may have to declare any bank account you used in Australia (if you had signature authority over it) on a Treasury form that you file separately from your income taxes - but that's a declaration only, just to tell them you had an overseas account during the year that had more than $10,000 at some point. (See Schedule B - there's a check box asking about foreign bank accounts, and if you check "yes" they tell you about the form you're supposed to file.)
Cheers,
Bev