The Trump campaign has consistently pointed to unauthorized immigration as the cause of a series of problems it says plagues the country. That is rarely actually the case.To former President Donald J. Trump and his running mate, the root cause of many of the issues in the United States is simple. Be it gun violence, high housing costs, long wait times at emergency rooms or an impending depletion of disaster relief funding, Mr. Trump and Senator JD Vance have offered the same diagnosis: All are because of unauthorized immigration. “The mass migration invasion has crushed wages, crashed school systems —...