I lived in the US for a few years. Most of these have been mentioned, just reinforcing:
Quality of life is very much tied to your income.
It's much more expensive than you'd think with health insurance and property taxes (can run into tens of thousands a year).
Health insurance is insane. People take jobs just for the insurance. I know adults with masters degrees still doing shifts at Starbucks in their 30s and 40s because they offer insurance. Imagine going to A&E with a broken arm and no insurance. That's at least $5,000 right there.
Everyone is on multiple pill prescriptions. Even young people.
Birth control pills are much harder to get and much more expensive.
Outside of major cities, it's very car-centric. You need a car to get anywhere.
The politics are ridiculous. As much as I dislike Tory policies over here, they do stillhave humanity and can be shamed into doing the right thing. I have many, many Tory friends who are lovely people. Republicans in the US are just fucking insane.
Food portions are massive. At first I was sickened, but you just keep getting served huge amounts soyou get accustomed toit. Even grabbing a 'small' bag of crisps at lunch, they are three times the size of ours! I really had to watch my weight.
Speaking of, the number of super morbidly obese is pretty sobering. I don't know anyone in the UK who could be a participant on My 600-lb Life. I saw candidates every single day in the US.
On the plus side:
Although it's gone down a lot, there is still much more social mobility in the US. More than in the UK, in my opinion.
If you do have insurance, health care is very very good.
Hawaii (the parts without people).