A would-be king wants a coronation on June 14, a date already laden with meaning: Flag Day, the 250th anniversary of the founding of the U.S. Army, and, yes, Donald J. Trump’s 79th birthday. But this year, Americans are refusing to let the day be coopted. Across all 50 states, from big cities to small towns, more than 1,000 events are planned to mark what organizers are calling the “No Kings Day of Defiance.”