Australia isn't a continent - it's part of the continent of Asia, as is the Marshall Islands. To distinguish it from mainland Asia, the region of Australia and the surrounding states is sometimes referred to as Oceania - whether the Marshall Islands sits in that region or not varies according to different sources.
Indonesia is a country made up of thousands of islands, but it is not regarded as "between" Australia and Asia as it is considered part of Asia.
Part of the Marshall Islands are a part of the US. (The islands of Bikini and Enewetak use to be US nuclear test sites.)
North America and Australia
Australia is a continent, an island, and is a single country. Asia is a continent composed of several countries and many islands that are part of a huge land mass. Asia is also joined to the continent of Europe.
North America has the arctic archipegalo in northern canada. There are quite a few islands in the archipegalo. Some organize indonesia as a part of the oceania continent or the continent of australia. This large group of islands would make the oceeania or australia have many islands. Although some categorize these islands as a part of asia.
Indonesia is on Asia (administrative), but Indonesia isn't exactly located on a continent. Indonesia located on group of islands between Asia and Australia, and the group of islands often called "Nusantara" in Indonesian.
No.
No. These islands are located between Australia and Asia. Indonesia and Philippines are a part of the Malay Archipelago.
The Marshall Islands were sold to Germany and became part of German New Guinea.
Asia
The southern part of Africa, all of Australia, half of Antarctica and some of the southern islands if Asia.