The US budget is 6.5T USD for 2022.
The US DOD budget was 753B USD for the same year.
The US Medicare program was 747B USD; with another 45B USD for NIH.
So the US actually spends about equal amounts on military and healthcare, at the federal level — about 11.5% on each.
A better question might be why the US gets so little ROI on its healthcare spending.