Specifically, what did they do with that expansion? Did they keep on rolling along gobbling up China (and others) as they went? Did they halt all advancements and temporarily put on hold the war(s)? Did they make peace and keep what they had?
The Japanese had reached stalemate in China by 1939, they were never able to progress far from that position for the rest of the war. China was a member of the Allies, they would have never made peace. They did gobble up southeast Asia, that was the entire point of Pearl Harbour.