WASHINGTON — Addressing a deeply divided nation, President Donald Trump called for a “new American moment” of unity Tuesday night and challenged lawmakers to make good on long-standing promises to fix a dangerously fractured immigration system, warning of evil outside forces seeking to undermine the nation’s way of life.Trump’s State of the Union address blended self-congratulation and calls for optimism amid a growing economy with dark warnings about deadly gangs, the scourge of drugs and violent immigrants living in the United States illegally. He cast the debate over immigration — an issue that has long animated his most ardent supporters — as a battle between heroes and villains, praising the work of an immigration agent who arrested more than 100 gang members and saluting the families of two alleged gang victims.He also spoke forebodingly of catastrophic dangers from abroad, warning that North Korea would “very soon” threaten the United States with nuclear-tipped missiles.“The United States is a compassionate nation. We are proud that we do more than any other country to help the needy, the struggling and the underprivileged all over the world,” Trump said. “But as president of the United States, my highest loyalty, my greatest compassion, and my constant concern is for America’s children, America’s struggling workers and America’s forgotten communities.”Trump spoke with tensions running high on Capitol Hill. An impasse over immigration prompted a three-day government shutdown earlier this year, and lawmakers appear no closer to resolving the status of the “Dreamers” — young people living in the U.S. illegally ahead of a new Feb. 8 deadline for funding operations. The parties have also clashed this week over the plans of Republicans on the House intelligence committee to release a classified memo on the Russia investigation involving Trump’s presidential campaign — a decision the White House backs but the Justice Department is fighting.The controversies that have dogged Trump — and the ones he has created– have overshadowed strong economic gains during his first year in office. His approval ratings have hovered in the 30s for much of his presidency, and just 3 in 10 Americans said the United States was heading in the right direction, according to a poll by The Associated Press-NORC Center for Public Affairs Research. In the same survey, 67 percent of Americans said the country was more divided because of Trump.