How long does it take to go from Boston to Australia?
Including a brief layover in California (most likely Los Angeles), a trip from Boston to Sydney would probably take 20-26 hours.
Australia is an island continent. The only way to drive to Australia from a another country is to either use a car carrying ferry boat that goes to Australia, or to drive an amphibious car, such as the WW 2 Ford DUKW, and go in calm waters a short distance. Almost everyone goes to Australia by plane or boat, they don't drive there.