I wouldn’t underestimate the cultural differences between the US and the U.K. which are often forgotten as we share (more or less!) a common language. That being the case, it might be worth thinking about universities with a large number of US students. I’m sure your child would make lots of friends of different nationalities, but sometimes when far away from home, it’s nice to know a few countrymen or women!
The obvious example, which is also a campus university, is St Andrews. It has the benefit of being located in an extremely beautiful historic little town with magnificent beaches (but Scottish weather!) and is extremely safe. Perhaps download a copy of their brochure wear/ prospectus to see if any courses suit . Their terms (semesters) are also more aligned to the US model than most U.K. universities.
Edinburgh also has a large number of foreign students and is a safe, prosperous city with excellent and safe public transport and a good international airport. It’s a good city for a reasonably well off student and a very pleasant environment. It’s certainly within a day trip visit of St Andrew’s too, especially if your child drives.
Nottingham is a campus university. Not a particularly pleasant city, but the campus is very nice.
You’ll find that university accommodation - ‘halls of residence’ are usually only available in the first year of the degree. Thereafter it’s usually a mad rush trying to secure a private rental with friends. It’s up to the students to organise this themselves - the uni doesn’t do that. Sometimes, parents are called upon to pay an entire year’s rent up front or guarantee rent. International students may also have to satisfy legal ‘right to rent’ checks with the U.K. Home Office ( look after immigration and right to reside in the U.K.).
Overall British universities treat their students like adults - they are generally a less nurturing environment than US colleges, perhaps because fewer students go on to post graduate studies. There is no culture of fraternity or sorority houses. Students make friends in their halls and on their courses in first year, in various clubs or societies they join, or in the university union (official uni clubhouse usually offering discounted drinks and snacks ) or local pubs. U.K. degrees are often vocational and not general in nature, conferring expertise in a narrower field (allowing a move straight from uni into the legal profession qualifying exam for example) rather than the broader base type of US college degree ( pre law etc) which will require further college based study thereafter.
Students may drink alcohol from18 and often do! British parents expect this and ‘have the chat’ about knowing your limits and the dangers well before the kids head off to uni.
If your child ends up in the U.K., it might be worth trying to find a relative, friend or other adult contact in the place they end up in, just in case of emergencies. I have been this person for a work distant acquaintance with an 18 year old daughter studying in my home city from abroad. It meant that she had one name to contact if very homesick, needing a steer where to buy stuff, or - as happened on one occasion - to sit with her in hospital emergency room after she broke her ankle on ice. I didn’t mind at all - she was a sensible girl, but like my own kids at 18, was reassured by speaking to someone else’s mum there on the ground, so to speak!