If you are a legal resident of the United States, you can purchase health insurance for your parents through the Affordable Care Act (ACA) Marketplaces. You may also be eligible for a subsidy to help cover the cost of premiums, as well as any out-of-pocket costs such as deductibles and co-pays.
If your parents are not legal residents of the United States, they are not eligible for coverage through the ACA Marketplaces. However, they may still be able to purchase private health insurance through a carrier in their home country or through a third-party provider that specializes in international health insurance.