The US national healthcare system is one of the most efficient, but also one of the most expensive. A bit like in India, many travellers come to the USA to undergo rare operations, at their own expense.
To enter the United States and receive medical care, it is advisable to take out a applying for a visa at the embassy nearest to you.
It is clear that foreign visitors are not covered by the American national health system. It is possible to receive medical treatment in a public hospital without having medical insurance, with the costs associated with such treatment being borne entirely by the patient. Some insurances may cover some costs.
Whenever a traveller seeks admission to the United States for medical treatment, the consular officer must obtain medical information on the nature of the illness or disability the applicant is seeking to treat. People with certain types of illnesses or disabilities may need special administrative treatment before they can obtain the right to re-enter the United States.
The immigration officer must determine whether the applicant has sufficient funds to cover all processing costs, and must be satisfied that the applicant will not be a public charge once in the United States.