Biggest sacrifice is my family is all US based, and the time zones really suck for staying in touch. The next thing would be the eye-watering compensation increases in the US in the last 5 years since I left. I'd be making significantly more income if I had stayed. That is something I still struggle with on a personal level.
What have I gained. I suppose a different perspective on the US, to some of the absurd Americanisms that I used to just accept: the crazy amount of patriotism and propaganda, the poverty, ghettos, widespread homelessness, the gun violence, the failing/overpriced medical system. The US is a really messed up country in many ways - it's sad given how wealthy it is and successful in other areas, and all the smart people, it shouldn't be like this.
The NHS is great, although it feels like it's gotten worse since I moved here. Still, everyone can get good quality medical care, it just takes time.
There aren't homeless people everywhere here. I can walk around the roughest parts of London, the worst that will happen is I might get mugged. In Chicago, there were gun shootings blocks away from where I lived with my small children. I went to Colorado over the holidays, and there had just recently been a mass shooting at the Boulder King Soopa which was closed. It feels so much safer here overall.
Europe is on my doorstep and I've spent some time traveling to quite a few different countries, and it's really enjoyable. COVID put a hamper on that for the last couple years, but the opportunities are there.
Pub food is really delicious in the UK. UK sausages are amazingly good. I miss steaks in the US though, although there are some pretty great places in London. Cider is awesome, and I can drink it even w/ my IBS issues unlike beer. Coffee in London is the best I've ever had.
Public transport is great and I can explore the city easily. I can walk out the door and go get groceries, or shop on the high street, or eat out. Not needing a car for every single thing is pretty great once you get used to it.
There's a large amount of diversity and I've met a lot of great and different people with unique perspectives that have given me new insights.
Squash is a great and fun sport and available to play pretty much anywhere without costing a lot.
It's not all roses though. Brexit. Tory austerity policy is bonkers. Quality of education has gone down a lot, I am struggling with this as my son goes through secondary. There is a bizarre class system perpetuated by widespread independent (private) education which gets subsidized via tax exempt status. NHS waiting lists are super long. Quality of services has gone down it seems - it is hard to find good community facilities and centers which aren't falling apart or overcrowded. Taxes feel absurdly high for what we get. Housing costs too much. US taxes can be a nightmare as an expat.