Additionally, you are falsely associating the minor differences in mortality and disease rates with other countries to healthcare.
Why is this a problem? You are ignoring demographics.
Canada and Australia simply do not have the same demographics of the United States. Neither Canada nor Australia has a massive African-descent underclass populating the inner cities, nor do they have over 20 million largely uneducated immigrants from Mexico.
This is only somewhat true. Canada has less dramatically poor people because it has a more extensive social welfare system.
But in reality, the number of Americans poor relative to the median isn't much higher than most developed countries in the world.