For now. Post Brexit, things can change. I’m sure Scotland can be bribed to take you along on the escape to sanity (you still make biscuits in Carlisle, right?)
Unfortunately, it’s not an animated diagram, so it will not be possible to show the full range of what is in, what is out , and what is being shaken all about.
Anyone who has looked at the diagram and thought- “This looks really complicated- I need more information before I can even begin to unravel this.” Well done, you’re at least two years ahead of the Westminster government.
Hate to say it but the commentators above are correct. “The matter of Britain” dates to when Brythonic languages were spoken in the islands, as well as Brittany (of course). Usage since then in the ‘different parts’ has just become more confusing. Is Wales part of England? Is Scotland? Denizens of either region would emphatically assert otherwise, but poor Mr Trump is quite correct. For example, soldiers from those parts are still galled to be called part of the English army.
Of course it’s officially called the “British Army” - but you will find it generally called the “English Army” on the continent, and such usage crops up everywhere in reports by ordinary civilians of eg. events in the second world war. Furthermore, whether Wales is altogether distinct from England is not so clear cut as you suggest. It is only a principality, not a kingdom. When Elizabeth I or Henry VIII declared “England is an empire”, meaning a sovereign state, they included Wales. England and Wales together still form the constitutional successor to the former Kingdom of England. Most tellingly, Wales follows the same legal system - including not just the English ‘common law’, but the machinery of justice also.
Scotland of course emphatically does not, and yet to the ire of nationalists Scottish troops are still frequently thought of worldwide as forming part of the ‘English’ army! This must be galling, but it’s still true, and is likely to remain so for some time.
On the contrary. Two examples may suffice: the first is a French re-telling of a joke (by a British officer) entitled, “sympas les grades de l’armée anglaise” (‘Kind of cool, ranks in the English army’). To which a user named “Tchetnik” (= Cetnik, a member of the far-right Serbian militia in WW2) responded, on 2nd June:
“Armée BRITANNIQUE, please, sinon, les Ecossais, les Irlandais et les Gallois vont placer une grenade DF dans votre lit.” [’…otherwise, the scots, irish, and welsh will plant a fragmentation grenade in your cot’].
Likewise, on 5th September 2016 appeared this sentiment by another French person: “J’aime bien les Anglais et j’apprécie leur compagnie et leur façon de vivre. Je connais très bien l’armée anglaise…”.
Furthermore, I can attest that such usage was the norm at least in Germany, France and Spain in the 1980s.
As a student (of mathematics) with a pronounced English accent (courtesy my primary school in Erith, Kent), I found myself constantly the butt of such remarks. Which felt quite bizarre: I am not in fact English, nor even British, at least not since 1962 with the coming into force of that year’s British Nationality Act. It did however mean that I noticed how common usage in nearly every European country was, and remains, to conflate English with British.