Even the uninsured in the US get healthcare treatment when they need it. Preventative care has been shown to have little effect on outcomes because the great bulk of it finds nothing. What you list are exceptions, not the rule.
No, they do not. Millions do not have health coverage, so they walk around with no healthcare at all. When they get too sick to continue, they go to an emergency. That is very expensive and way too late. We have millions with diabetes who do not get health monitoring. Many are not getting healthcare because employers do not provide it. Many workers are living on luck. It will run out.
Hospital emergency has to provide min. coverage to stabilize them. Then they send them home.