He returned to the United States in 1793 and established a law practice in Newport.

He was a member of the United States Federalist Party in the Senate, and served as chairman of the Commerce Committee from 1815 to 1817.

After leaving the Senate, Hunter continued to practice law in Newport.

In 1836, he was appointed by President Andrew Jackson to be the United States representative to Brazil.

One opinion that he is known for is that he believed that the state of Massachusetts was exaggerating its role in the Revolutionary War.