That is completely incorrect. As anyone who has been paying attention to the devs unheard of communication and transparency, one of the flagship, albeit controversial features of the game is that there is only 1 server that the entire world plays on. The only instances occur in the haven tutorial. The game itself runs off exactly 1 server located in England and is intended to remain so. There are lots of nuances regarding this issue and I highly recommend watching some of Henrik’s Twitch streams to understand this choice and the developer vision in general
Trust me I've watched dozens of hours of Henrik's streams, I know what you're referring to.
What Henrik has said over and over is that the game is and (until there is a new continent) will run on one "server", located in London, as you say, but I believe he's referring to "server' in the "World of Warcraft Server" sense, meaning a shared world that people play in, not a single physical box.
He also has gone intro extreme detail about the nodeline/node streaming architecture, and has described that population per node matters, that the reason there are stutters across nodelines and your horse can disappear/reappear across lines is because you are being transferred from one computer to another, and that they can redraw nodelines to improve performance in certain areas if they become routinely too populated.
In the last stress test for example, they purposely brought as many people to one location as possible, to see how many people could be loaded into and supported in a single "node", which is different from the overall population the world can handle, and different from the overall load the login server can handle (which has been the bottleneck in the first stress test)
The entirety of transferring between nodes and all of that (your horse disappearing and reappearing later) makes no sense if it's simply one computer. It is my guess (but put together from listening to copious amounts of info), that the entirety of the "server"/world is hosted in one datacenter in London, across multiple physical computers/virtual machines. Because they are in one datacenter means you can be transferred from one to another across a nodeline almost instantly. They can also assume almost instand communication between the different nodes etc (so you can see people across a node and their movement for example, and I'm sure it's necessary for the action combat system to assume 0 latency if you for example shoot someone across a nodeline or you are fighting an enemy and one of you crosses a nodeline). None of this would be possible if some people were logging into a datacenter in San Francisco and some were loading into a datacenter in London.
That is why he's said the only way they'd do another server location is if they make a new continent. That way they could re-create the structure I mentioned above in another datacenter, and when you travel/load from one continent to another, they move you across datacenters, but you can be assured everyone you're interacting with and areas you see are in the same datacenter.
It makes absolutely no sense in today's day and age for them to host a multi-thousand person MMO on a single computer, it would be extraordinarily limiting in terms of processing power and max population. They are almost surely cloud hosting the game, and having it spread across multiple physical computers in a single datacenter allows them to simply purchase more resources if they for example need to create smaller nodes to accomodate more players. Henrik has said they can redraw/spin up new nodes on the fly without rebooting (again supporting the idea that these are all in the same datacenter). Eve does the exact same thing, it's a shared universe, but they hide transferring between computers behind lightspeed traveling between systems as a "loading time" as it transfers you to a different physical computer.
None of this detail really matters though, and would just confuse people, which is why he says there is one "server". But I do believe that's the core reason they won't just make a US server at the moment. They put a huge amount of tech and energy to create a single seamless no loading time world spread across a dynamic series of nodes so that everyone could all play together, have the same shared experience and the world could scale to accommodate an almost limitless amount of players (as long as they purchase more cloud resources), why would they throw that in the trash and make another server somewhere else and split up the population?
As for Haven, yes each Haven instance is contained in a single physical computer, which is much simpler (no nodelines) and they can simply spin up a new computer/copy when one reaches capacity, then spin it down when they don't need it. They can't do that as easily as I described above for the main world if each node of the map is assigned to a single computer (they need to redraw the nodelines to add/remove computers, hence why they may need to pause purchases if the population ramps up too quickly).
