I have no experience or advice to offer, but I am very interested by what other people might say... Thanks for asking this.

Holidays are very different. People seem to take longer breaks in the winter than in the summer.

And generally get/take less holiday than European folks, but they have quite a lot of bank holidays

They tend to work longer hours too, from what I’ve heard

I have spent my last year and a bit doing this. Decisions are made after you've finished for the day. Americans blend their work/life a lot more e.g. my colleague's work calendars contain when they're exercising, etc. As a grumpy briton, their range of emotions confounds me. One moment they're crying, the next they're bouncing off the walls. Look for a company with a minimum for their holidays. Lots of US companies give out "unlimited" knowing full well that people barely use them. If the US company is a "good" one, expect their idea of good to still be low compared to UK standards. e.g. UK allows a lot more maternity leave than the US gives. # of holidays are likely to be low, even if they're high by UK standards. Pro-tip: Tell Americans about the place names around you, to Americans it sounds like you life in middle earth. Emphasize the age. It blows their mind and acts as a good icebreaker.

As an ex-Brit who has lived in the Bay Area, California for the last two decades, I'll second pretty much everything Dominic said. I'll also say that the US is not a cultural monolith so the style of interactions expected/permitted will vary quite a bit across the country. West Coast companies tend to be very "politically correct" (a phrase I hate but it's probably the easiest way to describe their interactions) so they are the most different from my experience of UK companies over the first half of my career. When I first started working here, I was taken aside a couple of times and told "that behavior/way of speaking is not acceptable here".

On a practical level, I think a lot of US companies tend to be pretty slow at paying contractors unless that is a normal way that they already do business with non-Americans, i.e., unless they have a lot of overseas contractors already.

And on the subject of payments, the US banking system is a nightmare. It still feels like it's operating in the 1960s and it behaves like a network of 50 different countries that don't like talking to each other. In fact, that applies to pretty much anything in the US that is "nationwide" -- don't be fooled into expecting it to work like just one very large country!

do you become liable to pay US tax if contracting for a US company but living in the UK?

or do you have to fill out a US tax form to show that you are not liable

My contract work with US clients was just short contracts with direct invoicing and wasn't subject to US tax, as I recall (but that was a while back). When I made the transition from the UK to the US, I had already switched to US salary (and therefore US taxes) and I just called up the Inland Revenue one morning and let them know the details, and never saw a UK tax assessment after that -- persuading the IRS (US) that you don't actually owe them US taxes is far harder and more complicated than just a friendly phone call!

I didn't fill out any forms, afaik the US isn't interested in me. I spoke to an accountant about it and it seemed fine.

US banking is nuts. $40 of my salary goes missing every month between what I'm supposedly paid and what shows up, I assume that some US middle-man is taking the fee.

We've had people randomly not get paid, or have significant delays. We switched provider at some point which resolved that.