Note that there is no US Embassy in Hong Kong or Macau and that this falls under the US Embassy in Beijing in China. There is however a US Consulate in Hong Kong and Macau for residents of this area. The contact details for the US Consulate has been listed below with a map, email address and also their telephone numbers.
You can speak to them about consular assistance such as marriage registration as well as birth registration, death registration as well as marriage registration. The Consulate is located close to Government House and not far from the British Consulate in Hong Kong and the Thai Consulate in Hong Kong.
US Consulate in Hong Kong & Macau