At the end of June, authorities in San Antonio, Texas, opened the back of an abandoned truck to find the bodies of more than 50 migrants inside – people who had made the journey across the southern border in extreme heat. The news led to scrutiny, from all sides, of the Biden administration’s approach to immigration, with Republicans saying it was too weak and Democrats, too harsh. Jonathan Freedland speaks to Silvia Rodriguez Vega and Pedro Gerson about the steps the US government could take to prevent further deaths at the border