It's capitalism to an extent, sure, but it's also the culture of a country.
Which I guess is to say yes, it is the culture of a country, and the culture of the US strikes me as money above all else.
It's the American emphasis on individual freedom that results in a lack of government mandates for healthcare. Nearly everyone has healthcare, adding the small percentage who don't to the existing government-run system would not be a major financial burden, and cases like the one you cited are effectively (but not literally) zero.
Historically, there's been a tug of war between people who feel like you should be able to take the chance of financial ruin over an unlikely event and those who think the state should be protecting those people from themselves, leading to the disaster of a system we have currently. That's pretty much the explanation.