This study estimated that socioeconomically vulnerable Canadians’ chances of receiving better health care were 36% greater than their American counterparts and this estimate was larger than that based on general patient comparisons (9%). One may wonder about the public health significance of such relative risks/protections. Attributions of risk/protection among populations are a function of three factors of which relative risk is only one. The size of the population and the prevalence of exposure to risks are also important. In this instance, the entire USA population is at relatively greater risk of receiving lower quality care, its more prevalent low-income and inadequately insured populations more so. Applying our findings to population parameters and attributable risk formulations we estimated that without reform, over the next generation more than 50 million Americans will be treated less optimally and die earlier than had they enjoyed a single-payer health care system like Canada’s.