American officials have blamed a legal threat for their refusal to meet Harry Dunn's parents.
Mr Dunn, 19, died after a crash outside RAF Croughton following which the suspect - Anne Sacoolas - fled the UK.
His relatives and local MP Andrea Leadsom wanted to discuss a series of road incidents said to involve US staff from the air base.
But the United States said a meeting would be inappropriate because the family intends to sue its government.
In a letter addressed to Ms Leadsom, Yael Lempert, deputy chief of mission at the US Embassy in London, said: "Regrettably, at this time we are unable to meet with the Dunn family directly or discuss specifics of the case surrounding their son's tragic death.
"The family's spokesperson has publicly announced the family's intention to make an imminent filing of a lawsuit against the United States Government.
"Given the strong interest of both countries to ensure proper judicial review, we have been advised that it would not be appropriate to engage in a discussion which might touch on that matter."
However, Ms Lempert said she would welcome the chance to meet Ms Leadsom and Col Bridget McNamara, RAF Croughton's base commander, to "discuss the steps that have already been taken" to improve driver safety.
Mr Dunn was killed when his motorbike collided with a car outside the base on August 27 last year.
Mrs Sacoolas - the wife of a US intelligence official based at RAF Croughton - sparked an international row when she claimed diplomatic immunity after the crash.
The 42-year-old was charged with causing death by dangerous driving in December, but an extradition request was rejected.