Pearl Harbor was about knocking out our carriers, but the carriers weren’t in port on December 7th. Had they been, it would have been a whole different ballgame.
Depends...
On December 7, 1941 the US had a total of seven fleet carriers and one escort carrier, of which two (Enterprise & Lexington) were stationed at Pearl Harbor.
On December 7, Enterprise was just returning from Wake Island and Lexington had just arrived near Midway.
Had one or both been sitting ducks in port and destroyed, the US still had Saratoga in San Diego, plus Yorktown, Hornet, Wasp, Ranger & Long Island in the Atlantic.
Of those, Lexington, Yorktown, Wasp and Hornet were eventually sunk in the Pacific.
The US already had several carriers in production, but the next ones available were Essex & Yorktown (CV-10) in early 1943.
So the big question is: had Enterprise and/or Lexington been lost at Pearl Harbor, what US carriers could have been available for the Battles of Coral Sea and Midway (May-June 1942)?
Hard to say, but here's something to keep in mind: after Coral Sea, where Yorktown was severely damaged, emergency repairs at Pearl Harbor quickly got her back into the fight in time for Midway.
So it's realistic to think that had either or both US carriers "sank" in shallow Pearl Harbor, they might well have been repaired and ready for battle six months later at Coral Sea.
Bottom line: you're possibly right about the war's early years, but by August 1945 the US had produced over 100 carriers of all sizes, and the war's outcome would not have changed.