Donald Trump's homeland security chief got a grilling during a congressional hearing into the administration's former 'zero tolerance' policy that created scores of family separations at the US's southern border. 'We are the greatest country in the world,' Elijah Cummings, the chairman of the House oversight committee, told acting homeland security secretary Kevin McAleenan. 'We are the ones that can can go anywhere in the world and save people, makes sure that they have diapers, make sure that they have toothbrushes, make sure they're not laying around defecating in some silver paper,' he told Cummings. The panel was looking into reports that unaccompanied children, many of whom were separated from their families, are being held in overcrowded, filthy conditions