Catherine Rampell: Don’t blame China, Mr. President. Blame the robots.

Mr. President, if you’re looking for someone to demonize for killing blue-collar jobs in your favorite industries, don’t blame China and “bad trade deals.”Blame the robots.Thirty years ago, the U.S. iron and steel mills employed about 188,000 people. Today, that number is about 86,000. Mindful of the suffering of tens of thousands of displaced workers, many of whom voted for him, President Trump is trying to turn back the clock with steel tariffs.This will do little to he