As Keir Starmer ponders how best to ensure that the incoming Trump administration remains committed to maintaining that relationship, the series offers some potentially useful (and historically accurate) food for thought.
Where season one explored a familiar popular culture trope - a transatlantic love triangle - season two turns its attention to matters of geopolitics.
Here is the story of an unusually close bilateral partnership, one which is informed by history (Churchill is often seen glaring from a painting in the ambassador's London office), shaped by the fear of a common enemy (Russia) and sustained by an apparent willingness to share just about everything.
Underpinning it all, says The Diplomat, is a common language and the strategic utility to Washington of Britain's position in the north Atlantic.
As Irish writer George Bernard Shaw once supposedly declared: "England and America are two countries separated by a common language". In The Diplomat - in which it is uttered at one point by Wyler - its underlying assumptions are certainly apparent. Matters of transatlantic difference in policy, perception and protocol, frequently emerge during heated conversations. Britons and Americans anger, antagonise and annoy each other.
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Yet despite the various disagreements the relationship nonetheless remains "special" throughout. In fact, the pacey dialogue (a la The West Wing, on which the series creator, Deborah Cahn, was a producer) ultimately delivers an assertive retort to Shaw's tongue-in-cheek quip.
Whether it's Wyler and foreign secretary Austin Dennison (David Gyasi), or vice-president Grace Penn (played by West Wing veteran, Allison Janney) and prime minister Nicol Trowbridge (Rory Kinnear), all the major protagonists, British and American, talk to each other with more than a hint of familial directness. In one scene, Penn actually has to stop herself from finishing Dennison's sentences.
This theme of linguistic connection, and especially the extent to which it is integral to the "Anglosphere", is particularly apparent in the final episode of season two, which was clearly inspired by the Aukus security agreement of 2021.
The key scene involves a celebratory dinner gathering of Anglosphere dignitaries in Britain. Much like the very real diplomatic fallout over Aukus, the Australians have angered Paris by cancelling a plan to buy some of their submarines in favour of a British-built design.
The British are delighted to have one over the old adversary. And the Americans are very aware that their presence at the rather chummy meal will almost certainly "piss off" the French.
Aside from a mutual willingness to annoy the French, what also emerges from this gathering - which very deliberately takes place at Blenheim Palace, birthplace of Winston Churchill - are the geo-politics which ultimately underpin the US-UK relationship.
As The Diplomat carefully explains, the eastern seaboard of the US is vulnerable to attack from Russian nuclear submarines. Indeed, all that stands between New York and oblivion, we're told, is a little island archipelago off the north-western coast of Europe: the United Kingdom.
In fact, what stands between is one specific bit of this archipelago: Scotland. But what if Scotland declares independence from the union? No Scotland means no United Kingdom, which probably means no US access to the fictional "Cregan" naval base (clearly a fusion of the Holy Loch facility, a US submarine base from 1961 to 1992, and Faslane, where the UK's nuclear submarines are currently based).
Such is the strategic calculus of the new cold war. And such, too, is the ultimate significance of the UK to the US, at least according to The Diplomat. The special relationship boils down to real estate. The UK has it and the US needs it.
As The Diplomat suggests, at the very heart of the transatlantic alliance has long been something essential to US national security: European air and naval bases. And these are strategic assets that the new president will surely want to retain.