Carl has eaten the fruit of the tree of Freedom.
Its over for him. He's returned to the hellscape of bongland with opened eyes.
This is an anecdotal observation, but I have an american friend who's studying in Europe and he was dismayed at how cold and introverted a lot of Europe is. It's not just Britain, practically all of Northern Europe, regardless of political affiliation, has that same attitude of aversion to strangers, that's taken to be as rudeness by American tourists (like cashiers not smiling, but having a blank expression). Where I currently live, whenever I travel by train or bus, there seems to be an unwritten rule that you should never sit next to somebody you don't know, unless there is nothing left but neighboring seats. So it's not uncommon to see throughout the whole train all the areas with 4 seats, looking at one table to be occupied by just 1 person. And this obsession with personal space is even worse in Finland, a country that has the infamous single seat public benches.
Meanwhile, excluding Britain and the Nordics, the introversion among the northern Slavs and the Baltics manifests in them taking people smiling at them with outright annoyance. It is not uncommon for people to pejoratively say "what are you smiling about?". It can range from something playful like "oh, did you get laid?", or them taking offense and thinking you are holding yourself from laughing at them. In post-soviet places, nobody smiles unless they have a clear reason for it (maybe that's why they love Ryan Gosling so much).
It wasn't until my friend went as far south as Austria that behavior of the crowds started to become familiar to that what he grew up with in the states and even then... when he went to Italy, Rome, he encountered one American girl that lamented how she missed the warmth and hospitality of her home country. So even the extroverted part of Europe may seem more reserved for certain Americans.
I don't think it's the recent political tension either, that can be best observed when contrasting and comparing British humor with American humor. It becomes very quickly apparent that British humor is substantially more morbid.
American:
British:
The way I'd explain it, for as much as I and many others like to mock and make fun of the Americans, they do possess that American exceptionalism of being the world's Golden Retriever, while we in Northern Europe are Black Cats. It's not that we hate people, we just like to have space, and unless we already know you, or you bring our equivalent to catnip - Alcohol, that we may start loosening up and get more giddy.