To anybody writing a web form that asks for my country --- or, for that matter,
anybody else referring to it in any way:
I am a citizen of, and resident in, the United Kingdom of Great Britain and
Northern Ireland. It is perfectly acceptable, and even encouraged, to
abbreviate this to "United Kingdom". (Historical note: before 1927, it was
officially the United Kingdom of Great Britain and Ireland; in practice, the
Irish Free State was independent from 1922.)
I am not a citizen of Great Britain. There is no such country, and has not been
since 1801.
I am not a citizen of England. There is no such country, and has not been since
1707.
Of course, Great Britain still exists within the UK, and England within Great
Britain. They are not countries, though. Americans, especially, should take
note that referring to the UK as "Britain" has been wrong for almost 208 years.
No part of Ireland has ever been in Great Britain. Referring to Northern
Ireland as part of Great Britain is always wrong, both geographically and
politically. It's not likely to win you any friends, either.
No part of Scotland or Wales have ever been in England, with the exception of
minor border changes. Referring to them as such is (almost) always wrong, and
also unlikely to win you any friends.
Finally, there hasn't been a king or queen of England since 1604, when James
I/VI changed the title to "...of Great Britain". Technically, after that point
both England and Scotland were ruled by the King (or Queen) of Great Britain,
though they remained seperate countries until 1707 (in personal union).
Not difficult, is it?