Despite their often obvious ethnic, socioeconomic, occupational, and religious differences, and the fact that most will never meet each other, the majority of people in the United States see themselves as members of a large community called "America." What concept does this demonstrate?

This concept demonstrates an imagined community.

Explanation:

This term was introduced by Benedict Anderson in 1983 to explain nationalism. An imagined community is imagined because an individual will never meet, know of or see every single individual within the community but he/she still identifies with it and in everyone's minds there will always be a sense of community and unison.

In this case, all the individuals from different backgrounds and obvious differences still see themselves as members of the larger community of "America", even though they will most likely never meet each other. This is an imagined community.