This population-based study compares U.S. effectiveness with 20 Other Western Countries (OWC) in reducing mortality 1989–1991 and 2013–2015 and, responding to criticisms of Britain’s National Health Service, directly compares U.S. with U.K. child (0–4), adult (55–74), and 24 global mortality categories. World Health Organization Age-Standardized Death Rates (ASDR) data are used to compare American and OWC mortality over the period, juxtaposed against national average percentages of Gross Domestic Product (GDP) Expenditure on Health (%GDPEH) drawn from World Bank data. America’s average %GDPEH was highest at 13.53% and Britain’s the lowest at 7.68%. Every OWC had significantly greater ASDR reductions than America. Current U.S. child and adult mortality rates are 46% and 19% higher than Britain’s. Of 24 global diagnostic mortalities, America had 16 higher rates than Britain, notably for Circulatory Disease (24%), Endocrine Disorders (70%), External Deaths (53%), Genitourinary (44%), Infectious Disease (65%), and Perinatal Deaths (34%). Conversely, U.S. rates were lower than Britain’s for Neoplasms (11%), Respiratory (12%), and Digestive Disorder Deaths (11%). However, had America matched the United Kingdom’s ASDR, there would have been 488,453 fewer U.S. deaths. In view of American %GDPHE and their mortality rates, which were significantly higher than those of the OWC, these results suggests that the U.S. health care system is the least efficient in the Western world.