U.S. and Japanese Aircraft Carriers WWII

U.S. and Japanese aircraft carrier strength and losses at the end of each year from 1941 to 1945

Source:  https://www.statista.com/statistics/1353080/wwii-japan-us-aircraft-carrier-strength-and-losses/

As shown by the graph, Japan had more aircraft carriers than the US at the start of WWII, 11 Japanese to 7 US carriers. Japan lost 5 carriers in the pivotal 1st year of the war, while the US lost 4. The first six months of the war were mostly Japanese successes. But the battle of Midway was pivotal, and the Japanese lost 4 carriers at the battle.  

https://en.wikipedia.org/wiki/Battle_of_Midway

American industry substantially out built the Japanese and in the later years of the war the US was much stronger.  But the existing US Navy beat the Japanese at Midway, and the Marines and Army won Guadalcanal, and the US was on the offensive for the rest of the war.