Donald Trump’s policies could leave the US more vulnerable to dangerous synthetic drug trafficking from abroad, even as the administration has vowed to stop fentanyl from entering the country, former government officials say. This week, Trump imposed tariffs on Mexico, Canada and China, ostensibly as a tactic to stem the flow of illicit drugs into the US. Jim Crotty, the former Drug Enforcement Administration deputy chief of staff, called the approach “coercive” and said it has the potential to backfire. Federal funding cuts could also leave US borders more insecure, according to Enrique Roig, a former Department of State official...