The U.S. government has suspended operations across their Application Support Centres run by the U.S. Citizenship and Immigration Services (USCIS). These centres are also used to submit biometrics for UK visas made from the U.S.A. Therefore, applicants will be unable to book appointments using these centres. The suspension will continue until at least 1 April 2020, however, we expect the suspension to continue post 1 April 2020.
The announcement initially stipulated that VFS centres, which are used for Premium appointments, were going to be made available to all applicants. However, a further update from VFS confirms that they too have closed all their centres across the USA until further notice.
Applicants are therefore advised to continue checking for updates before making their visa applications.