Sentence:  Nor is it an accident that baseball , growing into the national game in the last 75 years , has become a microcosm of American life , that learned societies such as the American Folklore Society and the <WSD>American</WSD> Historical Association were founded in the 1880's , or that courses in American literature , American civilization , American anything have swept our school and college curricula . 
Meaning of the word marked with <WSD> tags:  any number of entities (members) considered as a unit