One other point is our "nobody is turned away" policy. If a sick person shows up at an ER, it's illegal to deny them service based on their inability to pay. Michelle Obama, for example, made a lot of money finding ways to redirect these financially undesirable patients away from her affluent hospital.
Simple truth is that while we have plenty of people without insurance, we don't have masses of people being denied emergency care. The costs often end up covered by the government, adding to the high cost per capita as well. Illegals without insurance are estimated to account for $11B yearly in spending - that one group alone accounts for several percent of the cited per-capita government spending number.