What is the largest administrative district within a state in the usa?

The answer is County.

County is indeed the largest administrative district or political subdivision within a state (United States) that provides certain local governmental services. The term "county" is used in 48 states in the United States. Example of chief administrative divisions of a country or a state are known as Great Britain and Ireland

can you explain it better

answer; cindy crawford tina feycarrie underwood///meryl streep;