United Kingdom of Great Britain is a country off the coast of Europe. It consists of four countries; England, Scotland, Wales and Northern Ireland. The capital city is London. It is the home of the hero known as the Black Knight.
It was seen in "Meet Captain America", as a war broadcaster reports on the news on the frontlines of WW2.
And in "Come the Conquerer" as Kang's forces attacked all parts of the globe which included Great Britain.