Deputy Prime Minister David Lammy said he called US Vice-President JD Vance to tell him he was wrong about the murder of teenager Henry Nowak.
Vance blamed the death of the 18-year-old British student on the "mass invasion of migrants". He said the "only response" was " anger".
Lammy told the BBC he spoke to Vance on Saturday. He told the Vice-President the killing "has got nothing to do with mass migration".
The killer, Vickrum Digwa, falsely claimed he had been racially abused. He said he acted in self-defence after murdering Nowak in Southampton last year.
Digwa, who is British and was born in the UK, was jailed for life. He murdered Nowak with a blade.
Bodycam footage showed police handcuffing Nowak as he lay dying. Digwa falsely claimed to officers that he was the victim of an attack.
The killing sparked a debate about policing and knife laws in the UK. Violent protests erupted in Southampton.
Vance said on Friday that Nowak had died "the way a civilisation dies". He said authorities had "abandoned" and handcuffed him.
The killing was "tragic" and "enraging". Nowak would still be alive today, Vance said, "if the last few generations of elites had stood their ground".
In an interview with the BBC, Lammy said he called Vance to discuss his comments.
"I told him he was wrong, " Lammy said.
He said they had a "conversation. Lammy said he did not agree with Vance's views on civilisation.
Lammy reminded Vance that Nowak's family had called for calm.
"We remain colleagues and friends, " Lammy said.
Henry Nowak's father, Mark, appealed for calm outside the court. He said: "We do not want his death to be used to create division, hatred, or tension."
Lammy and Vance have formed a friendship. They have met regularly since entering office.
The friendship began when Lammy was an opposition MP and Vance had just been elected to the US Senate.
Summer Vance and his family stayed with Lammy at his home in Kent.
The US-UK relationship has been rocky lately.
Downing Street criticised "people trying to interfere in our democracy".
The Independent Office for Police Conduct is investigating Hampshire Police's response to the Nowak case.
The head of Hampshire Police said the force is "sorry for handcuffing and arresting Henry".
The National Police Chiefs Council document on anti-racism has come under scrutiny.
On Tuesday, the NPCC said it would review the language used in the document.
Reform UK's home affairs spokesman Zia Yusuf argued there was a link between police guidance and what happened to Nowak.
Yusuf said Reform UK would continue to make the argument.
When asked if he believed the police were institutionally racist, Yusuf said he did.
Lammy said, "We are all equal before the law". He added that ethnic minorities are disproportionately represented in the criminal justice system.
Lammy also said, "We've moved on from that period of racism" in policing.