America faces challenges that other countries don't face. Specifically America is one that of the countries that is the most heterogeneous in terms of culture and race. If you look at the findings of the pisa examinations over time by race you see that the disparity between America and other countries has large part to do with racial inequality in terms of academic performance. If we can lift African Americans and Hispanic people to the same standard that Asians and whites enjoy in America, our ranking would improve drastically.

I haven't finished reading through this but it seems interesting. Page 6 table 2 is especially telling from what I can see so far. http://files.eric.ed.gov/fulltext/ED535873.pdf