Why would you buy an Aussie Falcodore for $40k that depreciates at the same percentage rate as a $15k Hyundai? The chances of me ever buying a brand new car are basically slim to none, but if I did it wouldn't be anything but a Toyota or possibly a Subaru. Not everyone can just throw money away every 5 years.
No government will raise Tariffs on all imports to the point that Aussie cars could compete. That would be political suicide.