Some of the biggest names in UK construction were bidding for the job, each with a US partner, including Balfour Beatty, Laing O’Rourke, Mace and Skanska.
Work is expected to start on the embassy, which will be located near Battersea Power Station, in 2013 and be complete in 2017.
The 500,000 sq ft building is planned to be built at Nine Elms, near Vauxhall in London.
The 12-storey blast-proof glass cube sits on top of a colonnade, surrounded by a park and lake that some have dubbed “the moat.”