Go read the actual report: http://www.who.int/whr/2000/en/whr00_en.pdf
Only 37.5% of the ranking is even peripherally related to health care, namely health outcomes (measured by DALE, Disability Adjusted Life Expectancy) and responsiveness (how satisfied patients are). The US is #1 in responsiveness and #24 in DALE (4.5 years behind Japan at #1 and 0.5 years behind Germany at #22).
It's unclear how significant the gap in DALE is, since lifestyle and genetics strongly affect DALE. Fun fact: life expectancy for Japanese Americans is higher than for Japanese (84.5 in the US [1], 82.6 in Japan). Within the US, life expectancy varies from 44 (Lakota Men) to 86 (Chinese American Women), a gap of 42 years.
To actually rank health care, one would need to measure medical outcomes for specific medical diagnoses, adjusted for patient quality. E.g., it would need to answer questions like "given a group of non-overweight white males aged 45-55 with prostate cancer, how many survive at least 5 years?".
[1] http://minorityhealth.hhs.gov/templates/browse.aspx?lvl=2...