A transatlantic political row has erupted over the killing of a student in England, after the US State Department stepped into the debate and denounced what it described as “ideological conditioning and two-tiered policing” as evidence of a broader civilisational decline. The controversy centres on the death of Henry Nowak, who was 18 when he was fatally stabbed last year. As he lay wounded, police handcuffed the white teenager after his attacker falsely claimed he had carried out a racist assault. On Monday, his killer,…