American citizens are required to present a valid U.S. passport to enter Bermuda and the United States. Currently, Americans do not require a visa to enter Bermuda. The U.S. Customs and Border Protection and the airlines will ask to see proof of U.S. citizenship when you re-enter the United States.
Normally, a Consular Officer cannot intervene on the behalf of Americans traveling without proof of citizenship.
For further information please contact the American Citizen Services section of the Consulate.