In short, victory was never in doubt.

US always meant to fight a long attritional war against the Imperial Japanese armed forces. Greg Kennedy in his "Anglo-American Strategic Relations and Intelligence Assessments of Japanese Air Power, 1934- 1941" stated that even though Japan could and did innovated in the tactics and technological department. Japan never had any industrial capacity to main a long protracted war.

American understanding of Japanese tactical and technological innovations were not accurate at the start of the war. Because post 1930s, Japan starts to increase security in military intelligence. So new tactics and the capabilities of the the war machines of Japan were badly assessed. The Naval Attache Reports, from the 30s noted that the Japanese government was trying to combine different branches of their military that served the same function, so to address their underlying material insufficiency. British military attache to Japan at the time also noted, and the report was passed onto US, that Japan lacked sufficient ability to build reserves to replace losses. US Military Intelligence Reports also noted that even though Japan could copy and innovate based on western designs their production line was inefficient and that caused the cost of production to be much higher than in western nations. There are also many other reports on Japanese industrial capacity along the same line.

So even though IJN surprised the US at Pearl Harbor and some of their new tactics shocked the USN. Once the American war machine started to get into gear. Japan was quickly overwhelmed.

Edit: Japan had 10% of the US industrial capacity. I do not remember the source for this figure, if anyone knows, please post the details