Here’s things I know:
Canada pretty much wouldn’t take you, no matter your level of personal wealth, if you had a disability. They have rejected a billionaire with son with down’s syndrome. Here’s one story. But they supposedly reversed that in 2018, though I haven’t seen many stories about things changing a lot.
Canadian health care does make access to many drugs, surgeries, and hospitalizations cheaper; but it can be challenging (depending on province) to get access to some biologicals or things like HEP C treatment.
United Kingdom has an Immigration health surcharge you need to pay if you are on a visa anything other than tourist visa to live there to access public health services (that cost is still less per year than many Americans pay per month). It’s very hard and expensive to get a UK “indefinite leave to remain” (UK equivalent of a green card) as an American unless you’re in a particular field. It’s also not the cheapest to get. Here’s some details on costs:
As far as UK health care, while it’s free, mental health services are harder to access and many treatments that are par for the course here are not allowed under NHS. So, for example, continuous glucose pumps for people with Type I Diabetes are rarely allowed and need to be applied for by waiver, while here they’re quite usual.