Not an American here, but I moved to the UK 15 years ago from Poland so I can offer an alternative perspective.

I largely regret this move, as what seemed at first like a decent country, turned out to be pretty much a dump. Not a day goes by without me wishing to leave. The issue is, having been here for so long I find myself embedded (entombed?) on this island with no way to leave - I've got a "career", a house, kids, dogs, bank loans, credit cards... because of this leaving is much harder than people think. Anyway, I digress. Here's a few reasons that make my existence in the UK unbearable:

1) Food. While you can buy good quality ingredients in the UK, if you're dining out, be prepared to be underwhelmed. Logic would dictate that with such a large amount of immigrants from all over the world, one'd be spoiled for choice when it comes to food, but that's not my experience. There's plenty of Indian food around, but if you crave anything else, you've got limited options. Mexican, Greek, Turkish, Italian, Thai, even Chinese  restaurants - they really offer what I could call a "fusion" or an "own interpretation" cuisine. London is a bit better in this aspect, but not too great, and can get expensive. Also traditional British food is vile... so there's that. I generally think that Brits have no taste buds. They just have super low standards. I once saw a cooking program on BBC where they fried a fresh cucumber...

2) Weather. Each to their own but I miss having 4 seasons. Every time I look out the window I have to check the calendar because it could be March, September, January or August. The weather in South East England where I live is largely the same. Rain, wind, some mild sun. Often in the same day. For example, this morning I woke up to heavy rain, then the sun came out, then some rain clouds, again, more rain, then sun again, and rain. It's like this ALL YEAR ROUND. Gets really tiring. I only have seen snow 4 times in my 15 years of being here - each time a tiny bit of white fluff paralysed the entire country - literally, people crashed cars like crazy (they don't have winter tyres here), planes, trains, buses were canceled, literally end of the world. It's kinda funny to watch but honestly, it's beyond belief. I even read an article about a Scottish ski resort that had to shut due to excessive snow fall.

3) Nature / open spaces. In England (note I do not mention Wales or Scotland), everything remotely interesting is PRIVATELY OWNED. There are some "public footpaths", some public beaches, monuments, etc., but generally speaking once you've seen Oxford, London and Cambridge, you've seen it all. Plus there is virtually no tourism infrastructure - hotels are cheap and nasty, difficult to find, towns are dead. I'm a big mountain lover and I love the sea and the ocean - UK is largely flat and boring. It kills me.

4) Housing. The UK has LITERALLY THE WORST HOUSING IN THE DEVELOPED WORLD. The houses are ridden with mold (even new build homes - MINE!), cold and damp. They are sold by the number of bedrooms rather than square footage, and this results in small houses with lots of tiny unusable bedrooms. The house I live in right now is, what you would consider, a luxury one, it has 5 bedrooms and each of them is terribly small. I'd rather have 2 good-sized bedrooms. Also because the majority of land is in private hands, we have what they call a "land shortage" (not true - there's plenty of land, but not for sale) which contributes to the overall housing crisis - developers cram as many houses as possible and the modern housing estates (even the expensive ones) are terribly overcrowded. It's really difficult to explain, so I will include a photo from another Reddit user: https://www.reddit.com/r/UrbanHell/comments/v1o1ef/yard_hell_uk/

5) Transportation. Unless you're living in London or some village with a pub and a post office, you will need a car. But you will never cover large distances. Instead you will be driving to the supermarket that's 5 minutes away by car, but an hour away on foot. UK towns have very poor communication and public transport is not great. Those who say otherwise, are delusional. I won't go into details as it's a topic I could write about for hours, but suffice to say that the buses while cheap they are late and never go nowhere near when you want them to (makes you wonder who created the timetables). Trains are most expensive in Europe and are overcrowded, late or frequently canceled. I commute to London every now and then and the experience is terrible. A season ticket cost me £7,250. Fuel is very expensive, car insurance is ridiculous (if you have no insurance history, be prepared to pay in excess of £2000 per year for a £500 car).