Yes but if the main Aussie Army had been in the mainland, perhaps you wouldn't have been so quick to strike. This is all academics now for the historians. I'm sure grand papers will be written on the incident and how the Aussies screwed themselves by going after a vacation spot in Hawaii instead of closer, more ripe targets...
OOC: It's also a matter of how the countries are laid out and how armies and economics work. If you can capture a city you can basically hold it for ransom, hurting the enemy until the war is over and provided you have superior economics you basically win over time.
China lost 2/3 of its income in the opening attacks. With the way the rules are written for cities, you could never actually conquer the place but still effectively neuter them indefinitely as they would never have the chance to defeat you.