Reports suggest the move from Grosvenor Square to the new site south of the river will happen in 2017 - and already you can imagine that the new president and his minions will be having mixed feelings about the shift, not to mention many of his London-based officials who are actually going to have to work south of the river.
Unsurprisingly they will not include ex-pres Obama's choice, Matthew Barzun, who resigned in January. The job of representing Trump's admin in the UK will fall to a new, much older face. The 45th president has named fellow billionaire Woody Johnson, the 69-year-old sports fanatic, owner of the New York Jets NFL team, and heir of the baby-powder and pharma products firm Johnson & Johnson as his man in London.
Of course, this very rich man will not actually live here - he will have the super posh Winfield House in Regent's Park for his private life and his parties, and no doubt he could buy somewhere even grander if this did not suit him. Winfield House, by the way, is named after the founder of Woolworth's. It was owned by Woolworth heiress Barbara Hutton in the 1930s, and she gave it to the US government.
But what about Nine Elms? Well, the Americans are getting a big, super-safe, new building surrounded by lots of other big and blingy buildings. But the postcode - oh my dear, SW8!
The photo above shows the semi-translucent cladding that is going to cloak three sides of the cuboid structure. At first sight it looks like the sort of cheap and cheerful tie-on decorative facades favoured by some of the downmarket shops on Oxford Street. It looks temporary, like a strong gust of wind could send it flying.
But according to the architects this stuff performs vital functions in keeping the building cool and shaded in the summer, and also in deflecting the downdrafts of wind that can make life for pedestrians so bad. And the translucency is also meant to symbolise a transparency of government - apparently!
The architects, KieranTimberlake of Philadelphia, also wanted to avoid the fortress-like designs of many other US embassies: not sure if the big watery moat-like pond at the front of the building does much for that ambition. In fact the old embassy in Grosvenor Square was a very smart 60s building - have you ever seen so many windows in one facade? ANd all those rising bollards and so on only went in after 9/11. The old Grosvenor Square made a convenient rallying place for demos: the bleak wasteland of Nine Elms Lane is a much less attractive prospect for all, whether lovers or haters of the new regime.
However, it is no longer the 60s: you imagine Trump might quite the break from this Kennedy-era extravagance. The new Embassy, inits value-for-money postcode, is said to be one of the most environmentally-friendly embassies ever built. OK that's not the sort of claim that's going to impress the new boss, who doesn't care two hoots about the environment. He'll like the fact that it's cheap to run, but you wonder whether he wouldn't rather stay in Mayfair, protected by huge bollards and close to the gold-plated denizens of the Dorchester and the Hilton and the high-end nightclubs of Shepherd Market.
Well, the old embassy - a 1960 building designed by Finnish American architect Eero Saarinen – is going to be turned into a luxury hotel, so he could always hang out there anyway. Or he could just commandeer the Regent's Park house. There's room for two or three couples there, it seems.
Meanwhile, the staff of the new embassy will have plenty to explore in their lunch breaks and their after-work bonding sessions. There's the famously intense nightlife of Vauxhall itself, for example, plus some lovely (relatively) cheap eating places on Kennington Lane and Wandsworth Road. Maybe the secret gardens and lovely café of Bonnington Square will not be to every G-Man's taste - but of course it's about midway between the US Embassy and MI6, so they could arrange little meetings there.
In the summer a short walk or official car ride will take them to Battersea Park, one of south-west London's most beautiful open spaces. And already they have their very own Waitrose right on the doorstep.
But perhaps these dear Embassy folk will be discouraged from leaving their workplace, and will be kept happy in their sealed environment with Google HQ-style distractions. You know, non-stop free smoothies, a model railway to deliver authentic American burgers and/or sushimi to every work station, bean-bag-filled breakout areas, pool tables, Coke-fountains, wii screens, etc....and a pool of scooters on which to whizz around their new glassy home.
There's talk of a new pedestrian bridge, but where will that take them? Dolphin Square in Pimlico, approximately. Another place favoured by spies, apparently.
Talking of spies, if I had a high-powered telephoto lens I could spy on this new building all day and all night. Its massive bulk has blocked what used to be rather a pleasant distant view of Westminster's Victoria Tower from my bedroom window.