When Daniel Patrick Moynihan raised the issue of family structure half a century ago, his concern was the increase in black families headed by women. Since then, the share of children raised in single-parent families in the United States has grown across racial and ethnic groups and with it evidence regarding the impact of family structure on outcomes for children. Recent studies have documented a sizable achievement gap between children who live with a single parent and their peers growing up with two parents. These patterns are cause for concern, as educational achievement is a key driver of economic prosperity for both individuals and society as a whole. But how does the U.S. situation compare to that of other countries around the world? This essay draws on data from the 2000 and 2012 Program for International Student Assessment studies to compare the prevalence of single-parent families and how family structure relates to children's educational achievement across countries. The 2012 data confirm that the U.S. has nearly the highest incidence of single-parent families among developed countries. And the educational achievement gap between children raised in single-parent and two-parent families, although present in virtually all countries, is particularly pronounced in the U.S. Since 2000, there have been substantial changes in achievement gaps by family structure in many countries, with the gap widening in some countries and narrowing in others. The U.S. stands out in this analysis as a country that has seen a substantial narrowing of the educational achievement gap between children from single-parent and two-parent families.