The thing that's important to bear in mind is that the cost of paying for care out of pocket in Panama or any other of the countries listed here may well be as low as a co-pay in the US.
Many expats in Panama find that paying out of pocket for healthcare in Panama, with no insurance to help them cover costs, is still far cheaper than living in and paying for insurance in the States.
Many US expat retirees living in Panama do keep some form of Medicare so they can return to the US if they need anything major insofar as healthcare is concerned, to avoid long-term major costs and to be near family, etc.
Best,
IL Panama Editor Jess Ramesch