In a message posted on the embassy website Sunday, Jacob Walles pressed authorities to "carry through with its investigation" and try those responsible.
A month ago, thousands of protesters stormed the U.S. Embassy compound, tore down the American flag and looted and burned buildings, including a nearby American school.
The message emphasized it was the government's responsibility to provide security for "its citizens and guests."
Tunisia has arrested about nearly 100 people for involvement in the attack, charged with attacking the security of the state. According to their lawyers, some are facing the death penalty.