WASHINGTON, Feb 24 — Three men pleaded guilty on Wednesday of planning to attack power grids as part of a white supremacist plot to sow chaos and spark a race war in the United States, the Justice Department said. Christopher Cook, 20, Jonathan Frost, 24, and Jackson Sawall, 22, each pleaded guilty in a federal court in Ohio to one count of conspiring to provide material support to terrorists, the department said. “These three defendants admitted to engaging in a disturbing plot, in furtherance of white supremacist ideology, to attack energy facilities in order to damage the economy and stoke...