Finally, someone who is actually involved in the education system joins in. I've never been a classroom teacher, but I've been involved in education funding/policy issues for 30 years and I'll let folks throw two-dimensional charts and graphs out there that portray our educational system as being totally decrepit and sit back and laugh.
Three things to remember: (1) a lot of the high-performing countries have national curricula where textbooks and content are far more tightly governed than in the United States (try that one here), (2) the social safety net and access to high-quality early childhood health and education services is higher in a number of the countries that out-perform the United States on test scores and that creates a more equitable starting line for most students, and (3) in a number of the high-performing countries, there is much more ethnic homogeneity that creates learning environments where expectations are similar and barriers to learning are lower.
For a better and more accurate description of what I have presented, here's a link to Rutgers' education professor Dr. Bruce Baker's School Finance 101 blog: https://schoolfinance101.wordpress.com/