It's all manipulation, Americans are not quite as psycho and as selfish as we seem outwardly. In general, unless you're talking about bigotry and deep-seated prejudice, most of the dumb stuff Americans believe, we have been essentially force fed.
In this case, for historical reasons I don't remember ATM, it became normalized for employers to offer health insurance and for that to be the primary way people obtained health insurance. Combine that with the strategy to teach poor white people to hate on minorities, as a way to feel superior to someone and thus less angry about their own lot, and you can start to see how the link between employment and healthcare can be seen by some as a moral situation - the person without the good job to get the healthcare must be lazy, and since we don't want to encourage laziness, it's therefore acceptable (even preferred!) not to take care of them.
I can't stress enough how much effort is put into teaching a huge portion of America to fear and hate, constantly. We wouldn't be this bad otherwise, we're pretty normal folks by and large. Even pretty kind and generous, often. We've just been really fucked up, and very deliberately.