Where did you get the idea that the American Health care system is the best in the world?  

They consistently rank near the bottom of the list for developed economies and well below Canada whose rating is no roaring hell either.

It's not just about the percentage of Americans who lack coverage but the extent of coverage afforded to those that do.  Unless you have a gold plated plan, and few do, you will be restricted in most cases to the physicians and hospitals you can use and to the extent of treatment that you will get.

The great virtue of American health care is that it treats the rich and poor equally: the poor through neglect; the rich through plenty.  Both methods are likely to cause harm.