Ireland
It is not. It is called "An island nation" because of the fact that the island and nation of Great Britain are one and the same.
Great Britain (aka: England)
England isn't hosting the Olympic Games now - Britain is and the host nation team is called Team GB. The games were previously held in Britain in 1908 and 1948.
Great Britain (England, Wales, Scotland and Northern Ireland.)
A nation
Great Britain, or United Kingdom is not a country, it is a nation that is made up of England, Northern Ireland, and Wales No Britain is not a country on this island the 3 Country's are Wales, Scotland & England in the United Kingdom
England is a nation within the sovereign state of the United Kingdom (or more properly, the United Kingdom of Great Britain and Northern Ireland).
The first nation to build its economy on capitalism was Great Britain. Laws were changed to allow free trade in England and elsewhere in Great Britain.
In the beginning, Britain was basically fighting to defend itself all alone. There were Americans that joined the RAF, but as a country the USA did not join till much later in the war. Russia was fighting the Nazis too, but could hardly be said to be defending Britain, they were spending all their energies defending themselves. After the USA joined the war, they were the primary nation to defend Britain.
England
It was England.