Should the U.S. go the Australia route?
Hell no. (No offense to the great nation of Australia, which in this particular regard is just like a number of other countries.)
The right to abstain is not often celebrated, but that doesn't make it less important. Being able to save one's vote for when it really matters, and thus signal by voting that one has a higher degree of interest in the election outcome, is no less valuable than the ability to express a preference for one candidate or party over another -- and it's something that Australians (and Brazilians, etc) obviously don't have.
What evidence do you actually have for Australia being a great nation? If none, then why did you say it?
Today is the midterm elections in the United States, and I am not voting.
For the vast majority of elections, voting is irrational, because the individual's vote is proportionately very small. This means it cannot have an effect on the outcome.
There are, however, conditions which can lead to voting becoming rational, and these are: