White people in the U.S. aren’t just the “rich” subset of the whole population. They are reflect a complete spectrum, from poor to rich. They’re equivalent to Koreans in Korea or Japanese in Japan. Other groups in the U.S. aren’t just economically different, they’re sociologically different in dimensions that don’t really exist in Korea or Japan.

For example, 71% of hispanics speak Spanish at home. That reflects a group that’s comprised mostly of immigrants and their children. That poses additional challenges to education, beyond the economic differences. Poor whites in the U.S. and poor Koreans in Korea may have educational challenges from being poor. But that poverty isn’t layered with being raised in a household with immigrant parents who are in an unfamiliar country and probably don’t speak English fluently. That’s an additional layer of challenges that needs to be accounted for in comparing across countries.