Japan was fighting a war of attrition with the United States, and Admiral Yamamoto knew it from the beginning. He told the Imperial General Staff that he could promise them 6 months of victory following Pearl Harbor and after that, nothing. He knew the US had the industrial capacity to out build Japan by a factor of 20-1, even with us fighting Germany at the same time.
All the US had to do was keep the Japanese in check long enough to allow our forces to be built up to a level where we could go on the offensive.
But Japan did make a lot of mistakes, excluding having Pearl Harbor be a surprise attack.
- They should have launched the 3rd and 4th wave against Pearl Harbor to destroy the dry docks, fuel storage depots, and submarine pens. This would have crippled the Pacific Fleet far more than the loss of some old battleships.
- They should have kept their carriers together, not split them off into separate operations, especially when the US was expected to oppose. The temporary loss of Shōkaku and Zuikaku at the Battle of the Coral Sea (Shōkaku was heavily damaged and Zuikaku had it's air group shot to bits) and one light carrier sunk, it reduced the Japanese fleet's available carrier numbers to four fleet carriers, one medium carrier, and two light carriers. This should have been more than enough to deal with the US Pacific Fleet. However, they sent medium sized carrier and one light carrier on that worthless attack on the Aleutian Islands which meant that the Midway operation only had 4 fleet carriers available, and one light carrier. The end result was the loss of 4 fleet carriers at Midway. There were a lot of other tactical errors made at Midway, but that's for another time.
- They did not rotate their carrier pilots back home to train replacements like the US did. They kept them on the front lines until they were killed or wounded too badly to fly. As we killed their experienced aviators, they had no worthwhile replacements, while the US was constantly churning out pilots who had been trained and prepared by the veterans who had already fought the Japanese.
- Their land forces did not embrace new technology like the United States did. Most Japanese soldiers ended the war using the same bolt action rifle they started with.
- Fighting a land war in China did not greatly reduce the number of troops they had in the Pacific. Excluding the Kwantung Army, Japan still had around 4 million men in the army during the height of the war. While many were in other areas such as Burma, Thailand, etc., they still had well over a million to oppose the US island hopping campaign. What doomed those troops was the lack of naval support. Either they were wiped out in an invasion, or left to starve as we moved past and used them for bombing practice.