In America do commercial airlines have to have at least two pilots in case one pilot gets a heart attack or seizure mid flight?

I remember when I was inside a small aircraft with around a 100 people or less passenger capacity while flying from Seattle to Vancouver for a connecting flight back to Toronto. One of my concerns was we might not have a back up pilot on the aircraft since the airplane was so small and airlines might want to save by skipping that feature. Our designated pilot was obese and very old and I was worried he was at risk of a heart attack mid air. It's also possible the pilot wasn't that old but looked old due to obesity and bad skin.

In America do commercial airlines have to have at least two pilots in case one pilot gets a heart attack or seizure mid flight?
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