McALLEN, Texas (AP) — Immigration enforcement on the U.S.-Mexico border was plunged deeper into chaos over President Donald Trump's reversal of a policy separating immigrant children from parents, causing uncertainty for both migrant families and the federal agencies in charge of prosecuting and detaining them.A senior Trump administration official said that about 500 of the more than 2,300 children separated from their families at the border have been reunited since May.