Medical insurance : how to cover cost of er visits but don't have medical insurance?

Must have insurance: E.R. Care and hospital care is so expensive in the U.S. That only the wealthy can afford it without insurance. Many people go bankrupt or nearly bankrupt if they have a significant illness with a prolonged (>2 weeks) hospital stay, because the hundreds of thousands of dollars is paid by themselves. When the money runs out, patients can get medicaid-type (medical in california) health "insurance".