[JALU3]

The problem with that logic is that Japan lacked the doctrine to attack merchant shipping . . . and that japan lacked the infastructure to support a long term submarine anti-shipping campaign in the Eastern Pacific.
Therefore the nations of Australia and New Zealand would have continued to be supplied.
What Japan was focused on was getting to the resource rich dutch east indies. The reason for attacking the US and the Commonwealth was that they feared that both contries would have attacked them in response to their take over of the dutch east indies. Therefore they made the strategical decision to deal with the problem at the beginning of their campaign before either country could martial up their resources and provide a determined resistance.
Theoretically Japan could have attacked Commonwealth forces in the Far East, and with enough diplomatic tact, could have kept US Forces out of the war for another 3-12 months, if not longer. By that time, Japan could have consolidated their holdings in the Dutch East Indies and focused on China and India.
Those in the Japanese leadership knew that once America was focusing their full attention on them, that their long-term situation was in peril. That's why they attempted Pearl Harbor to attempt to get the US off guard and take us out of the war early.