Neither of them are false.
As of 2017, the US spends 17% of her GDP on healthcare, which is the highest amount out of all countries. The only reason that US healthcare is not considered top tier, is because of the comparable prices to other countries, in which the US prices are extremely expensive.
As of 2017, 64.1% of Americans over 65 have Medicare or comparable private insurance that covers them. This definitely means that there are less than "most" Americans over 65 that do not have health insurance.
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