Exactly. The entire Midway operation was intended to cause a fleet battle to wipe out the remaining US carriers/large fleet units, on the assumption that a threat to Midway/the Aleutians would draw them out of Pearl. And the operation was set up because of the face lost by the Navy when the Doolittle raid happened. No Doolittle raid, no Midway operation. The original plan didn't go out that far. As far as the Coral Sea battle that might not have happened, there could have been some consequences of that. First, Port Moresby might have been taken, and second, the Guadalcanal/Tulagi Japanese might have gotten started on an airfield quicker if they hadn't been bombed by Yorktown planes. Either could have made things take longer to defeat Japan, but, it wouldn't have stopped the US from doing so. I don't think there were ever plans to do more to Australia than isolate them. Japan simply didn't have the troops to take the Australian continent, and they knew it. So, while losing all the carriers might have made the Pacific war bloodier, longer, and more expensive, I don't think the Japanese could have stopped the US Navy once they started receiving all their new ships in 1943/44. It would have just delayed it a bit.