If you are an expatriate living in the US, additional medical coverage should be purchased for the period that you will be in the country. You will want to ensure this coverage protects you in case of an accident, a medical emergency as well as repatriation. You should investigate if you will need this insurance before entering the country and if the insurance needs to come from your home country, the U.S. or both!
Types of Coverage: All of the health plans sold through the Marketplace are offered by private insurance companies and are required to meet minimum requirements. All of the plans are required to cover a comprehensive set of benefits that includes hospital care, doctors’ visits, emergency care, prescription drugs, lab services, preventive care, and rehabilitative services. Before choosing a plan, individuals will be able to see whether their healthcare practitioner participates in the plan’s network (if choosing a network plan). Individuals will be able to choose the plan that best meets their needs and budget. Individuals with low-incomes may instead qualify for free or low-cost coverage through Medicaid or the Children’s Health Insurance Program. 
The National Association of Insurance Commissioners (NAIC), the National Governors' Association and "several insurance and consumer groups" opposed the AHP legislation.[80] The NAIC issued a Consumer Alert regarding AHPs, as proposed in Developing the Next Generation of Small Businesses Act of 2017. H.R. 1774.[80] Their statement said that AHP's "[t]hreaten the stability of the small group market" and provide "inadequate benefits and insufficient protection to consumers."[80] Under AHPs, "[f]ewer consumers would have their rights protected, "AHPs would also be exempt from state solvency requirements, putting consumers at serious risk of incurring medical claims that cannot be paid by their Association Health Plan."[79]

If you are relocating the United States, it is important to know that the US does not require all expatriates (or US citizens) to have medical coverage. However, the risk of being in the US without medical coverage is massive hospital bills or even no access to medical care. There are newer requirements for certain expats on select visa types that may require you to have health coverage.

Health insurance in the United States is any program that helps pay for medical expenses, whether through privately purchased insurance, social insurance, or a social welfare program funded by the government.[1] Synonyms for this usage include "health coverage", "health care coverage", and "health benefits". In a more technical sense, the term "health insurance" is used to describe any form of insurance providing protection against the costs of medical services. This usage includes private insurance and social insurance programs such as Medicare, which pools resources and spreads the financial risk associated with major medical expenses across the entire population to protect everyone, as well as social welfare programs like Medicaid and the Children's Health Insurance Program, which both provide assistance to people who cannot afford health coverage.
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