In 2025, Henry Nowak, an 18-year-old white man, was handcuffed by police as he lay dying from stab wounds after his killer falsely alleged a racist attack.
The killer, a Sikh man, was sentenced on Monday to life in prison.
Video showed officers ignoring Nowak's pleas as he lay dying, sparking questions over why the police had believed the allegation of racism and not Nowak who said repeatedly that he had been stabbed and could not breathe.
The case has sparked widespread anger in the country while populist political leader Nigel Farage and tech billionaire Elon Musk have amplified the charge that Britain has "two-tier policing" where fears of being called racist have led to ethnic minorities being given greater protections than others.
"Ideological conditioning and two-tiered policing are glaring symptoms of civilisational decline," the US State Department said on X.
"They must be rejected across the West.
"The United States sends our condolences to the family of Henry Nowak and the people of the United Kingdom at this troubling time."
Prime Minister Keir Starmer has said police had serious questions to answer about their handling of the incident, including how accusations of racism informed police thinking, and an investigation is taking place.
But he condemned a violent and disorderly protest that took place on Tuesday night and said it was "unforgivable" to exploit the death to stir tension after Farage called for people to respond with "pure cold rage".
He also told Musk to stop interfering in British politics on Thursday after the tech boss posted repeatedly about the case and said it showed that police were biased against white people in Britain.
The police reject accusations of any bias, but police chiefs have said they will review guidelines that were drawn up in response to decades of well-documented incidents of racism in policing, on how officers should treat ethnicities differently.
Nowak's family, who met privately with Starmer on Thursday, have described his treatment by police as "inhumane and degrading" but said his death must not be "used to create further division, hatred or tension".
Deputy Prime Minister David Lammy told Sky News on Friday that he welcomed the fact that the US government had extended its condolences to the Nowak family but said he did not recognise "this caricature of Britain having a two-tier criminal justice system".
