In the United States, Donald Trump's return to power is worrying undocumented immigrants and the groups that support them. Memories of mass deportations, detention centres and the systematic separation of children from their parents at the border during Trump's first term are still vivid in people's minds. So what will his second term mean for immigration? In California, "sanctuary cities" like Los Angeles, San Francisco and Berkeley are bracing for the human and economic impact of potential mass deportations targeting two million undocumented immigrants in California alone. Our US West Coast correspondents report.