You have gone from a hypothetical to concluding that people in the US die because they can't afford cancer drugs.

If your dad was over 65, he would be on Medicare. If he was younger than 65 and impoverished (income between 0 - ~150% of poverty level) he would be on Medicaid or another state plan for low income people. If he's above 150% of poverty level he probably has health insurance available at work or thru ACA. In fact is legally obligated to.