You can visit the US embassy in Bermuda in Devonshire. If you need to register a marriage in Bermuda then the embassy will be able to assist you in this regard. You can also ask about the services of a public notary and about applying for a US visa such as a K3 visa or K1 visa if you are not an American citizen.
If you have lost your passport or it is full then you can speak to them about adding pages to your US passport of apply for a new passport. The contact details and a map to the embassy has been listed below. There are also the telephone numbers, street address and the email details for the US embassy in Bermuda.
US Embassy in Bermuda