The rest of the developed world has single payer healthcare with results that are generally comparable to those in the US.
The rest of the developed world has _universal_ healthcare. In many countries it is provided through single-payer, in some it is through mandatory private insurance, in others it is a mix.
Where the United States stands alone is not the lack of a universal government program, but that we have many millions of people not covered by any health insurance system at all.