I don’t think the question is whether you view healthcare as a privilege or a necessity. I view it as both.
Being provided healthcare when needed is a necessity in the sense that it is necessary for you to live. Under US law a person cannot be refused needed medical care at an emergency room.
But health insurance is privilege. You must be treated but you will receive a bill afterward. Not paying your bill is not a necessity and no one else can be morally required to pay your bill for you.
All that being said, I actually support Medicaid for all (aka single payer) along the lines of the Israeli model (the Canadian model is not as good). The quality of care will decrease but people who want higher quality of care can pay out of pocket for better doctors or better insurance. I support this, not because it is a necessity or a right, but because the US is a rich enough country to provide it and why shouldn’t they. The US will spend billions of dollars to rescue US citizens being held hostage by a terrorist group. But if the same citizens are dying of cancer, the US shouldn’t pay millions to save them?