While the US does spend the most on healthcare, making healthcare free would not reduce costs. In fact, the "Medicare for All" act would actually raise costs by $32 trillion, and increase taxes by 20%.
This strain on the economy would only make a bad situation worse, especially during the Covid crisis.
Preventable deaths are not the fault of the US healthcare system; it is the poor health choices and habits of the population which causes preventable deaths.
Reducing preventable deaths would indeed lower emergency medical care and decrease costs, but reforming the US healthcare system will not reduce preventable deaths. Educating the population on proper diet, exercise, and the dangers of drugs, alcohol, and tobacco, will.
For-profit systems encourage competition which ensures only the best healthcare stays in business.
Growth in the medical field depends on competition to drive medical scientists and doctors to discover life-saving breakthroughs.
Free, universal healthcare is not cheaper and would be more of a burden on Americans than a help.