Why America was not yet outbuilding Japan in 1940-41

Why was the United States not already outbuilding Japan in 1940 and 1941?

Isolationist politics delayed action, and much of the initial effort was building the shipyards and infrastructure needed for the later surge.

Congress and much of the American public still believed that the war could remain distant, delaying authorization for a full naval expansion. Once mobilization began, a large share of early effort went into shipyards and supporting infrastructure rather than finished hulls. That sequence was industrially sound because later mass production depended on expanding capacity first. The weakness was timing: starting the same investment earlier would have brought the output surge forward.