Why Alaska was not a shortcut to Japan

Why did the United States not build up Alaska and take the apparently shorter route toward Japan?

Because Alaska was a difficult logistics route, and sea transport could carry the same supplies more directly to operational destinations.

Building up Alaska did not create an efficient direct road to Japan. Moving men and matériel through the region was itself logistically complicated. Once supplies were loaded aboard ships, carrying them toward an operational base was generally more useful than unloading them into another difficult overland system. The exchange illustrates why geographic distance alone is a poor measure of campaign feasibility.