If you are in Vietnam then the US Embassy in Vietnam is located in the city of Hanoi. Note the contact details for the Embassy listed below as well as the contact details for the US Consulate in Ho Chi Minh City. You can ask about assistance as an American if you are in need of consular assistance.
US Embassy in Hanoi
The US Embassy in Vietnam does not deal with question about the US fiancee visa or the US marriage visa or even the K2 visa. You are best advised to seek assistance from a law firm in Vietnam for this. The United States Embassy in Hanoi is the diplomatic mission of the United States in Vietnam. There is also a Consulate in Ho Chi Minh City. The Embassy is located at No. 1 Calmette Street, Ba Dinh District, Hanoi. The Embassy provides consular services, including visa processing and American citizen services, to residents of Vietnam and neighboring countries.
See also the US Embassy in Bahrain as well as the US Embassy in Belize.
See also other Embassies in the region. The US Embassy in Singapore as well as the US Embassy in Thailand. There is also the US Embassy in Vietnam as well as the US Embassy in Japan and US Embassy in Indonesia as well.
Details for US Embassy in Hanoi
Address: 7 Lang Ha Street, Hanoi, Vietnam
US Consulate Ho Chi Minh City
Address: 4 Le Duan Blvd., District 1, Ho Chi Minh City Vietnam