It is this decentralization and localization of schooling in the United States that creates, in fact, most of the problems for comparing American schools and students with those in other nations. For example, the United States may be incomparable to other nations because of its lack of any national standard for teacher training or certification. An even more important distinction between the United States and other nations is the highly unequal levels of funding and resources between school districts in America. The nested relationships of students, schools, regions, and nations make national comparisons of global citizenship education using straightforward descriptions misleading, as well. Yet, regarding cross-national comparison, discussions about the most appropriate comparative method have often been theoretical and abstract rather than practical or applicable to the study of the global citizenship education.