There are several possible answers.
Korea, which was divided into North Korea and South Korea following World War 2.
Vietnam, which was divided into North Vietnam and South Vietnam following the first Indochina war. Following the Vietnam War, they returned to being one country.
India, which was divided into India and Pakistan (East Pakistan and West Pakistan). Later, Pakistan became two separate countries, Pakistan and Bangladesh.
Korea
One European and two Asian nations were divided: East & West Germany; North & South Vietnam; North & South Korea.
Korea
It might be argued it is also divided into two nations by Capitalism: North & South Korea. And no, before you get excited I am not in any way suggesting the folks in the north are better off, manifestly they are not. Neither am I content in the idea of North Korea being a Communist country, it is, was, ruled by a despot.
Germany
Russia, china, and the two koreas
After the first Indochina war, Vietnam was divided into two nations, North Vietnam (Communist) and South Vietnam (anti-Communist), based on the Geneva Accord. After South Vietnam's army fell at the end of the Vietnam War, the two countries became one.Note: Korea was also divided into two nations following World War 2, but the division was based on plans developed by the United Nations which partitioned the country along the 38th parallel, with the Soviet Union adminstering the northern part and the United States administering the southern part. The politics of the Cold War resulted in the 1948 establishment of two separate governments, North Korea and South Korea.
Australia is a nation all on its own - there is only one nation in Australia.
The continent of Australia has just one country, and that is Australia. The country's official title is the Commonwealth of Australia. The nation of Australia is divided into six states and two territories.
north Korea and south Korea
There are two nations on the Korean peninsula because after the Korean War, Korea was divided into two different nations, namely North Korea and South Korea.
Bhutan, Nepal or Tajikistan
India and China