My experiences of the USA have come from both a family & professional standpoint. I have a naturalised relative in Texas & I've worked (albeit briefly) in the USA. It's better to think of the USA as 50 mini countries inside a larger bloc, similar to but not quite as strategic as the EU.
Geography:
Spectacular & intensely beautiful but also has extremes from desert to tundra & all in between.
Population:
The big cities are generally more centrist/left leaning politically. Some cities have VERY rough areas that are well publicised about.
Rural areas are traditionally more conservative & less government involvement, even in famous Democrat states like California & Colorado.
People:
Generally friendly, especially when you start talking & you have a British/European accent. Some of my relative's friends in Texas are very conservative but also some of the most hospitable people I've ever met!
Rights:
Poor employee/worker's rights (that vary by state) but average only 5 days holiday versus 25+ in the UK. No institutionalised healthcare so be CERTAIN to take out health insurance when you're over there otherwise you'll be broke quickly!
This is the big problem with actually living there, and is enough to make me not seriously consider the possibility - there would have to be a very, very, good reason (such as a dream job which was so good that I wouldn't care not having much holiday). Didn't realise they had a mere 5 days holiday, that is bad. Gives you very little time to enjoy life, it's a wonder many don't go completely crazy. You can't even have one two week holiday per year, and Christmas (despite the popular depiction) must be a very transient festival indeed; IIRC they don't even get Boxing Day off. The health issues I've already commented on.
Transport:
Car rules! The North East, California & Chicago have decent train/transit networks & buses but other than that it's very much having to rely on 4 wheels although the Interstate System is a wonder in itself.
This is the other big issue (for me personally) with the USA, though if I was to live there I'd learn to drive so it's not as insurmountable as the health / workers' rights problems.
Some places are completely unreachable by public transport, and that meant, for example, that I was unable to fully see the wonders of Washington State (of which I believe there are many).
A bit of planning and research, and perhaps luck, does allow you to get around by public transport. Greyhound is the major provider, though (in 2004 at least, not sure about now) they had this infuriating policy where a bus could be full - but you could not book it in advance. In other ways, planning a journey was difficult. This was something I was unaware of before going. Thankfully I mostly got lucky but did have to hang around the small town of Grants Pass, OR, one day waiting for a later bus.
I also visited Manitou Springs, Colorado (to climb Pikes Peak) and got lucky in the sense that in that particular year, there was a frequent all-day high quality bus service between Denver and Colorado Springs ("FREX" - Front Range Express - with free wifi). Sadly it didn't last and now it's just back to infrequent Greyhounds. Amazing that the two largest cities (I think) in Colorado have such poor connections. By contrast, Denver itself has a very good, continental-style, cheap (it was then), publicly-owned public transport system. Colorado Springs though is a
really strange place. Lots of skyscrapers, big empty streets, and very little in the way of shops. Well-known for rampant conservatism, I believe, but nearby Manitou Springs was much more laid-back.
The other form of public transport you get in the USA takes the form of something which is a cross between a bus and a taxi. You get these minibus shuttles which leave at set times, but have to be booked (otherwise they won't run) and are rather more expensive than regular buses. I used such a service to reach Summit County, Colorado from Denver and also used one in Oregon south of Portland - wanting to divert inland for a bit to see some of the interior (with rather varying results, I think in retrospect I should have gone down the coast).
Talking of Portland I found it (only stayed one night) a very laid-back kind of city almost with a bit of a European vibe.
Finally one surprising experience was the lack of taxis in rural areas. I stayed in Summit County (which had an excellent and completely free bus network) but one day wanted to climb a peak not on the bus routes (Quandary Peak) and thought I'd splash out on a taxi just for the one day. I remember trying to arrange it the day before but it seemed impossible to find a taxi which was free at this time! So I never did climb this particular peak.