Does OZ owe it's freedom to the US?

With respect to Oil fields under Japanese control during the war this page may be of interest:
Oil Fields and Refineries Under Japanese Control

 

While it might have been tactically wise, would it have been strategically wise?

When WW II began in Europe FDR instinctively knew that the US would have to enter the war. Unfortunately for the President, the American public had no interest in the affairs in Europe. For some two years FDR conducted a master class in how a democratically elected leader can sway public opinion into doing something they didn't want to do, often by the narrowest of margins. To be fair he had considerable help from Berlin and Tokyo, even London helped make a case for rearmament and drifting to armed intervention.

Only problem was the US public was not quite there yet, and nor would it act without a direct provocation. Let us consider the world situation and it was dire. German armies were driving deep into Russia, with nothing seeming able to slow them. England might be safe but the Atlantic was a concern. Greece and Crete were unmitigated disasters, and Rommel was driving on Egypt. There were whispers that Churchill didn't have the stuff to snatch victory from stalemate and maybe someone new was needed. Now Japan was moving into position to take what it wanted from the SRA and there was nothing meaningful Britain and her Commonwealth could do to stop it.

Morale is a powerful thing. It can't be calculated scientifically like planes, tanks and ships but it is as important to victory as the tools of war. You have to believe you can win as well.

If America had done as you suggest, if it had made it clear to Japan that if they didn't shoot at Americans what they did elsewhere was of no concern to the US, how would this be taken by the people of Great Britain, her Commonwealth, Russia, occupied Europe?

FDR had also to consider American public opinion. In that last summer and fall of peace Americans had begun to accept that war was probable, but there was greater willingness to confront Japan than Germany. FDR might see that Germany was the greater threat but he could only do what the American populace would allow him to do. He could not unilaterally say it's Tuesday, I think i'll declare war. He needed Congress and they needed the will of the people.

For Churchill and Stalin the choices politically were now pretty simple, fight and prevail. For FDR they were more difficult, he had to manipulate levers whose effects he could only dimly perceive. He had to keep the public focused on the stakes lest they conclude one day they were so strong they need not fear what Japan or Germany might do and could safely sit this out.

There was a strategic issue as well. Japan and the US understood each others intended strategic goals. Japan intended to seize the SRA and then construct what they hoped to be a impenetrable line of defenses that would shatter any attempt to breach. Thereby forcing Britain and America to accept things as they stood. America could not allow Japan to take what it wanted and then allow it build a defensive barrier. Not with a war that had to be won in Europe first.

We know how hard it was to wrest away Japanese conquests as it was, how much tougher would be if they were allowed 6 months to a year of US peace to build them up. Our most bloody battles were fought well after we had both a qualitative and quantitative superiority over Japan.