President Obama’s open border policy is providing the ultraviolent El Salvadorian gang MS-13 an opportunity to expand its operations in the US. And the gang’s founding members learned their murderous craft fighting as Marxist insurgents in the jungles of Central America; Dinesh D’Souza’s new documentary “America: Imagine a World Without Her” explores the dark new world taking shape thanks to Obama’s staunch anti-Americanism.