That's because mortality rates are only weakly correlated with healthcare quality. The US has much higher death rates in some young demographics, which skews the average, but those people didn't die due to lack of medical care.
You can have exceptional healthcare quality and relatively low life expectancy in the same population.
The Brown study I cited above concludes differently, and is strictly a longitudinal, retrospective cohort study involving adults 50 to 85 years of age.
Within that 50-85 cohort, among 73,838 adults (mean [±SD] age, 65±9.8 years), the participants in the top wealth quartiles in northern and western Europe and southern Europe appeared to be higher than that among the wealthiest Americans. Survival in the wealthiest U.S. quartile appeared to be similar to that in the poorest quartile in northern and western Europe.
You can have exceptional healthcare quality and relatively low life expectancy in the same population.