Domestic insurers should be able to cover visits to overseas facilities.
Health care can be good and cheaper in other developed countries. And health care in private clinics and hospitals can be OK and much cheaper in middle-income and even in low-income countries. For some US residents and citizens it might be a good deal to get an OK health care in a developing country than NO care at all at home, especially if local insurance covers treatment overseas. We could actually see a sort of specialization in international health care markets. For example, certain countries (even developing countries) can become specialize in some types of dental care procedures, etc.
That has many possible implications, such as:
1) Possible price equalization in international health care markets at certain margins.
2) More incentives for the development of health clusters in developing countries.
3) A reassignment of resources in the health sector in the US.