"US cut off oil & imposed sanctions on Japan in the years before Pearl Harbour."
You failed your history test there.
The Americans didn't start the war. WW2 was already well on its way before the US chose to side with the Allies against the Axis.
The Japanese were already deep in China, Germany and Italy were trying to conquer western Europe.
Once when the Americans took an active part in assisting the Chinese against the Japanese, the Japanese took the fatal step of attaching Pearl Harbour.
