Zheng He is correct that the Japanese were pretty much locked into carrying out the offensives that had already been planned. But I would think that there would be no Midway type battle until later on. The Saratoga was torpedoed attempting to rendezvous with the Enterprise no Enterprise no rendezvous. The problem is how quickly can reinforcements arrive from the Atlantic Ocean. The navy could send the Yorktown and Wasp both were fully operational. As for the Hornet she was just starting to workup in the OTL she did not got to the Pacific until march. You might be able to slice off some of the time but not much that is if you want a trained crew on board the Hornet. As for the Ranger I don't know if the navy would be willing to risk her in the Pacific. So the harassment attacks that the American carrier engaged in and so annoyed the Japanese would not happen until later. Doolittle Raid would not happen, so Yamamoto would not be so able to force a Midway operation down the throats of the rest of Japanese High Command. But Coral Sea would still be likely to happen.