I lived in the UK for a few years without setting foot upon Great Britain. I knew where I was at. I even knew what country I was in, unlike you. It is a shame you did not learn anything while you were there.
You should try to tell a Catholic from Northern Ireland that they are British and see how far you get.
And they still issue passports which correctly identify the nation-state as the United Kingdom of Great Britain and Northern Ireland.
In cr #2825 you said "Great Britain exists as a nation-state." You were wrong then and you are still wrong.
Great Britain is an island. Colloquially it is sometimes used as the name of the country, as the Encyclopaedia Britannica suggests ("although the name Britain is sometimes used to refer to the United Kingdom as a whole").
And in case you missed the post to GOPc, the term "Great Britain," as used in its present form, is attributable to James I of England.