Harry Dunn, 19, died in a hospital of multiple injuries from the head-on crash of his motorbike with a car on August 27, 2019 in Northamptonshire in the East Midlands of England.
The US State Department has confirmed that the driver Anne Sacoolas, 42, was the spouse of a US diplomat assigned to Britain, who then left the UK using her diplomatic immunity.
Friday's development comes after the Crown Prosecution Service (CPS) announced last month that they had charged Sacoolas with causing death by dangerous driving, metro.co.uk reported.
Confirming the extradition request, a spokesman for the Home Office said: "Following the Crown Prosecution Service's charging decision, the Home Office has sent an extradition request to the US for Anne Sacoolas on charges of causing death by dangerous driving.
"This is now a decision for the US authorities."
Dunn family spokesman Radd Seiger said they were "pleased" with the latest development and felt that it is a "huge step towards achieving justice for Harry".
"This will not of course bring Harry back, but in the circumstances of all that this family have been through, they are pleased with the development and feel that it is a huge step towards achieving justice for Harry and making good on the promise that they made to him on the night he died that they would secure justice for him," Seiger added.
Following the accident, Sacoolas was twice interviewed by Northamptonshire Police - once on the day after the crash, and on another occasion by officers who travelled to the US, reports metro.co.uk.
But under the Vienna Convention on Diplomatic Relations, families of diplomats are granted immunity from arrest or detention, with the sending state able to issue a waiver of that immunity.
According to the CPS, the immunity does not apply to dependents of consular officials based outside of London.
( With inputs from IANS )