If Americans lose their job do they immediately lose health insurance? /u/unclear_warfare No such thing as stupid questions

For example if you lose your job on Monday and get hit by a car on Tuesday and need an operation at hospital, do you suddenly need to pay tens of thousands of dollars or does your insurance continue for a few days / weeks / months?

For example if you lose your job on Monday and get hit by a car on Tuesday and need an operation at hospital, do you suddenly need to pay tens of thousands of dollars or does your insurance continue for a few days / weeks / months?