Their strategic goal was a diversion of U.S. forces, which is why i said it was successful. The forces diverted, however, were not a significant contribution of men and material, however, which is why i said their strategic victory was sterile. The Japanese had almost seven million troops in China, Indo-China and Burma, and only a very small force of Englishmen and Americans were detailed to deal with this--in Burma, where the Japanese had more forces guarding the communications than were in actual, combat contact with the Slim's and Stillwell's forces. A huge amount of Japanese force was basically left hanging out to dry in China, Formosa (Taiwan) and in Indo-China, where they were needed to guard either military resources (such as the air bases on Formosa) or strategic supplies. Burma was most important to the Allies as a base for air operations. Kenney's South West Pacific Area Air Force command was the major resource for attacking Japanese strategic supplies--they didn't care if they took out or occupied the mines or the refineries or the oil fields, so long as they prevented the shipping from making it to Japan. After late 1943, when the Navy finally got a decent torpedo, the USN submariners did the final noose tightening around Japanese supply lines. In every situation in which the Japanese had seized real estate for the strategic minerals or for petroleum, they were obliged to occupy the territory to protect the resources. Judicious use of air and naval resources allowed the Allies to interdict the flow of supplies to Japan without actually being obliged to fight the Japanese troops on the ground. This is essentially what MacArthur did in the southwest Pacific area, which is to say to bypass major Japanese forces, taking bases from which to attack them from the air, and to cut off their supply lines. That, of course, ended when he landed in the Philippines and had to attack them head on. But basically, millions of Japanese troops, using up enormous amounts of supplies (lotta rice to feed that many bellies) were hung out to dry, contributing nothing to the defense of the empire.
The attack on Alaska was an attempt to divert American forces in the same way, but it was far too small-time to have any significant effect. Probably the most important thing it accomplished was to divert naval and naval air forces at a critical time, but in the balance, even that proved insignificant.