I'm British. Lived in the USA for six years: three in Manhattan, three in Seattle. Moved to the Netherlands in late 2020; currently living in Utrecht.
Downsides:
The most obvious sacrifice is financial: I took a substantial pay cut to come here, and, on top of that, I now pay more tax. The day-to-day cost of living is a bit less in Utrecht than in Seattle, but not (nearly) enough to compensate. That doesn't make much direct impact on my disposable income — I have more than enough to live on from month to month — but it does mean I save substantially less.
House prices are out of control here; buying a house that we like feels like an impossible dream.
It's also harder to meet people and make friends. Part of that is Covid-related, of course, but the language issue makes it hard to join groups, clubs or activities — although my neighbours can speak effectively perfect English when necessary, that's understandably not how they want to spend their down time. That's compounded because most people my age are well embedded in social networks already, so it's hard for a newcomer to make connections with them.
I miss the landscape of the Pacific Northwest. The Dutch flatlands don't really compete.
Upsides:
The level of visible poverty is much lower. I found the level of homelessness, begging, deprivation, in the places I lived in the USA to be genuinely distressing. That's much less of an issue here (not zero issue, but much less).
Similarly, the level of visible inequality is lower. Sure, there are rich people and poor people in the Netherlands, but the differences feel less stark. Even the fairly poor have a decent standard of living. This makes me feel much more comfortable. I should add: neither this point nor the one above it are intended to minimize the plight of people living in Europe who are really struggling.
There's a safety net. I was well paid in the USA; I had good health insurance, etc. But there are enough “gofundme” stories of people who were in a similar position, and for health or whatever reasons it suddenly all goes wrong and they need help to deal with whatever life throws at them. Here, I'm pretty confident that if I or my family are suddenly unable to work, there's a safety net and we won't be out on the street. (In practice, if it had all gone wrong in the USA, I'd have escaped back to the UK, but you take my point.)
In general, infrastructure feels more solid. The road surfaces are better (seriously, American roads are terrible). Trains well-kept and reliable. Public spaces are clean and well maintained. Banking systems feel like they are decades more modern.
A good standard of education is fairly ubiquitously available to everybody, without costing a fortune. Although I save less, I don't have to worry about how I'm going to afford to put my kids through college.
Evens:
I biked everywhere in Manhattan, in Seattle, and now in Utrecht. I have never owned a car. I guess I failed at my American integration!