Georgia has multiple National Park Service sites, but no National Parks. Almost every state (maybe every state except Rhode Island?) has 3 or more NPS sites, but National Parks are a more specific designation.
Meanwhile tiny little Tasmania having 19 national parks... (though one is entirely inaccessible and one is practically inaccessible, reducing the number to 17).
In the U.S., the majority of national park preserves and protected lands aren't national parks, but national areas of a different type (national historic parks, national monuments, national historic sites, wild and scenic rivers, etc.). For example, Oregon has one national park (Crater Lake) but 10 protected parklands that are part of the national park system. Is the ratio similar in Australia? So would I assume there's 190 other national park sites in Tasmania? Or do they structure things differently? If it's different, it might not be that meaningful to compare directly.