Because the Japanese blinked. They lost a light carrier, We lost a heavey carrier Lexington and had Yorktown badly damaged and nearly missed Midway due to the damage. They got cold feat and pulled back. GOD helped us out at Coral Sea. IMO.
Instead, they were subject to over a hundred bombing raids by the Japanese. It was extensive, especially in the North of Australia.
The Australians loved the USA until the left in Australia imported so many immigrants to the Australian cities, where they outvoted the Australians who had experienced WWII.
The IJN’s most significant material losses were there pilots and planes, they lost significantly more than us and that helped to balance out our losses in ships.
They also lost an oiler. Poor sucker was misidentified by a scout plane as a carrier and the USN blew it out if the water with a full coordinated air-strike (a major mistake for us).