Gwen,
I hope you can be where you are more comfortable, soon. It's tough to live somewhere that you feel you hate. You start to find reasons to hate it even more every day. (Been there, done that.) Which just makes everything worse. I have a few comments about the USA vs UK, though.
Trash/litter. I lived in several places, all across the USA. In some (mostly back East) the trash littering problem was really bad. I can remember visiting in New Jersey/NY after having been away for a couple of decades and that was the thing that hit me first when we were driving away from the airport. Yuck. It wasn't like that in SoCal or Texas. And it's not like that where live in Scotland. (Thankfully, because I really hate generic trash strewn around.) Having taken a bus trip or two by accident into the poorer parts of town, I see litter. It seems definitely to be a class thing. There are people paid by the local council who come around my neighborhood and tidy it up every few weeks - raking leaves from the gutters, sweeping the streets, and then the other day there was a gent washing the glass at bus stop.(!)
Same with dog waste. In some neighborhoods here people seem to uniformly pick up after their dogs. I've been in other parts of town where you have to keep an eye on where you're walking. Considering the number of dogs that apparently live in this city, though, it's not bad. Although I have to say that I live in a block of flats. We all share a communal green space - where the young children often play - outside. The fact that people turn their dogs loose out there to crap and pee, even though they pick up the poop and bin it, is just...gross. Very young children play out there in the same grass, for goodness sake! Could people not curb their darned dogs, pick it up, and then let them run around in the yard to get their ya-yas out, rather than just turning them loose and then standing there on their cellphones until the dog comes back to go in the house? And then there's Cats. The obsession with allowing cats outside annoys the peewaddin out of me! Traffic. Foxes. Disease. Killing of Songbirds. Crapping in neighbor's gardens. Serenading at 2:00am. Marking their territory on your door or car or front steps....There are sooo many reasons to NOT let a cat outside and so many reasons to keep a house cat IN the house. But the cat rescue place insists we have a garden into which we can let a cat out before they'll let us adopt? That's just insane. I've had multiple indoor-only cats for decades in the past, and they almost uniformly lived to be extremely elderly, in comfort and safety. Without being a public nuisance. Our last girl made it to a week short of 21 years, and died from having gone on a hunger strike when the Daughter went away to University.
Medications. I am not an idiot. I do not need someone to read the instructions on how to use Naproxen or to inquire as to why I am purchasing it. That's my own business. Heavens... I try to remember that they are just following the training they have been given, but oy! For prescription medication, for me it's free here. If I didn't have good (expensive) medical insurance in the States I might have to go without it. I can put up with a lot of condescension (is that a word?) for free medications.
The sidewalk space thing. I can see where it would just drive you up a wall. My Daughter just hates it - she is of smaller stature than me and says it happens to her more often because of her size. It was much worse when we traveled to tourist towns or went south to England. Apparently people will generally move out of the way for an older person here. (Or I am intimidating, I don't know which.) But usually we both give way a bit. I have slammed shoulders with joggers, however. They uniformly are young women with headphones on who are obviously not aware of their surroundings, and since I'm a large person they are the ones who bounce. Annoying, though. Having been on a University campus for most of my later working days, when the influx of Chinese students began, I ran into it really bad in the States. Especially the cutting in line thing. There are cultures (like the Chinese) where disregard of the personal-space bubble is just rampant because that's not how it's done where they live. I always try to keep that in mind, but I hated it there and I dislike it here. But, again, I must look intimidating, or have learned to ignore it, as I don't seem to notice it very much anymore. I do keep my hand on my purse in a crowd, though. Just as I would in any large city.
The Empire thing. I think that must be worse in England, as the people I've met in Glasgow have been uniformly nice and friendly. They meet eye contact and smile back. As to lines, I keep having gents offer to allow me to go first when we both get to the till at the shops, or get on the bus, etc. That's probably an age thing, though. Even the younger people will offer to give me their seats on the bus if we are standing-room only. Which is lovely (I usually decline), but I'm not THAT old. People here still hold doors open for each other.
Driving. I compare here and Los Angles. I'm happier on the roads here, by a longshot. Although driving here terrifies me because everything, while seeming so similar, is different and I can't rely on all the "automatic" kind of driving behaviors that are ingrained after driving in the US for decades. In fact, it's hell trying to unlearn them. There's less drive-by shooting here, too, on the road. (And in general. Actually, there isn't any here.) People in California drive like maniacs, "go with the flow", and consider traffic signs to be basic advice only.
Work. Thankfully I was able to retire early so I don't need to work here. But I have been looking, just the same, and aside from the problems of being old and foreign, the strange insistence on "qualifications" is intensely irritating. You could be a world-famous brain surgeon, but if you don''t have the right certificate from an accredited agency that shows you sat through three mindless months of "this is a bandage" training to learn how to apply a bandage, you cannot be hired to apply a bandage. (Exaggeration, yes, perhaps, but it seems to be a common mindset. They don't seem to "do" transferrable skills here. If you haven't already done task "A" at a job, even though you've done tasks B,C, D, E, and F, several of which are very similar to "A", you can't get past the "sifting" to an interview. Maddening!)
Efficiency - the lack thereof. Oh, dear Lord, don't get me going on that one! It's staggering.
The Daughter just read your post and wonders if you live near a university (ak vomit in the streets land). That's one of the reasons we live a bit farther away from her Uni than we could have. To avoid the drunks. There really is a lot of drinking here. But there was in California as well. Encouragingly, it seems that more young people are NOT going into the drinking culture than in the past. One can only hope that persists. It's been a little uncomfortable to be teetotalers in a world of excess alcohol. But it was in States as well, so...eh.
But yes, perhaps you would have been happier checking out different parts of the USA, rather than making a huge cultural jump to another country. As time goes on in the USA the general culture is becoming more homogenized. I can remember traveling as a child and teen and how different the deep south was from the Northeast - it's not quite like that now. But there are enough different subcultures in the USA still that if you wade out of what is familiar you can experience them.
You know, books, TV and movies can lull one into thinking they know a culture - all the BBC dramas, etc. - and it can be a shock when you're immersed in it and find it's not that way. Apparently there's a syndrome in Japan where young women become besotted with all things French and then go to Paris and have such a tremendous letdown that they have mental breakdowns. I strongly suspect it happens to people moving to the USA from foreign countries sometimes, too. TV, books, and movies are not everyday life. Plus, it takes a certain personality type, I think, to be able to bounce around to different cultures and find happiness in them. Not a better or worse, just different. It's not for everyone.
Good luck when you get "home" again. Hopefully you'll be more comfortable when you are surrounded by the predictable and familiar. At least you will have had the experience, and won't find yourself sitting 20 years from now saying "gee, I wish I would have..." or "I wonder what it would have been like?"