In my experience as a former care-home worker (a long time ago, but one of my sisters works in one in the same area) and my impression from TV and real-life experiences of friends in the US, this is one area where the US and UK are very similar. For example, when in Florida I visited my American friends father who was in what they called a care home because he had terminal cancer. It was funded partly by the state, I think (by way of grants rather than directly), and partly by a religious organisation.
Only a few months before that my Grandad had died in a very similar place in the UK, except we called it a hospice. A hospice is a place where some people with terminal conditions get care and treatment; a lot of the people there will die there, but not all - some are there for temporary care and will leave to go home for at least a while.
The hospices I saw in both the UK and the US were excellent and all I’ve heard makes them sound the same.
For “care homes,” they can be for older people who are somewhat ill but not terminal, nothing requring extensive medical care, or they can be for people with serious illnesses, and then they’re usually called nursing homes.
The former tend to be private, expensive and not very good even if you pay for the best, but also not terrible unless you’re very unlucky. They pay their staff very little but the staff try hard and sometimes they’re skilled beyond their job - immigrants who can’t get nursing acccreditation in the UK, for example. I think there have been scandals about care in homes in the UK too; MRSA is one of the biggest problems.
IME residents mostly suffered from having to share rooms and other institutional aspects of the home, like there was communal underwear because having to sort out each residents’ underwear, with so many changes and washes, would have been very difficult. In practice we tried to keep them separate (by knowing which room the underwear came from) but we couldn’t guarantee it. It’s dehumanising even if it’s not intended to be.
Nursing homes vary a lot and can be quite good, but do have their own problems; they’re often state-funded which increases the care standards somewhat, but they’re still provided mostly by private companies - even if they’re not profit-driven, they’re still not state-owned. My step-nan’s nursing home refused to call by her “real” name, Marge, only using the very different name on her birth certificate, which she hadn’t used since she was about 10. The excuse was that the staff couldn’t learn two names, which made me think there was no continuity of care. I don’t think they helped her Alzheimer’s by calling her by the wrong name.
Like UDS says, there are national standards for all the types of homes, but I think there are in the US too (or, rather, state standards). IME the care home (not nursing home) I worked in would be astounding on the day of the visit and not so good otherwise.