President Donald Trump embarks on the most important trip of his presidency today confusing America’s friends and foes. In the days running up to Tuesday’s on-again, off-again, on-again summit with Kim Jong Un, he has defended Russia, given China a break and toyed with inviting the North Korean dictator to his Florida resort — all while trashing America’s European allies and imposing tariffs on this country’s closest trading partners that will cost American jobs. It is a bizarre warm-up even for him as Trump meets his bombastic match on the global stage.The summit with Kim is risky enough, given the impulsive nature of the two leaders, and the high expectations the White House has raised over a meeting where the goal posts for success seemed to have moved much closer. Trump should have used the last week building leverage by gathering a consensus among the allies over a united strategy for dismantling the North’s nuclear program. Instead, he soured relations by threatening the allies with a new round of tariffs even as he heaped praise on Kim and brushed off suggestions he needed to study up for the talks. He called for Russia’s re-integration into the global fold, and he threw a lifeline to the Chinese telecommunications giant, ZTE, which U.S. officials have accused of being a national security risk.Trump’s call Friday for Russia to be reinstated to the Group of Seven major industrial nations — made only hours before his arrival at this year’s meeting in Quebec — was another spiteful statement expertly timed to rub the allies the wrong way. The leaders of France and Canada already have signaled they will work around the president, a troubling development that won’t help the talks with North Korea or any effort to contain an escalating trade war.France and Canada said they will use the G7 event to highlight opposition against new U.S. tariffs on steel and aluminum imports. French President Emmanuel Macron called a meeting Friday with German Chancellor Angela Merkel, British Prime Minister Theresa May and Italian Premier Giuseppe Conte, saying these nations needed to "reforge the European front." The poor state of relations seems destined to isolate the U.S.; Trump groused about even making the trip and announced he would leave early to fly to Singapore ahead of his meeting with Kim.Trump’s eagerness for a deal with North Korea cannot cloud the larger vision for American national security. And pandering to his political base by imposing tariffs only costs American jobs. The New York Times reported Friday that an internal White House analysis on Trump’s trade agenda, which has not been released, concluded that the tariffs will hurt economic growth.If this president is sincere in his championing of American interests, he should find a way to do it without sacrificing the very foundations for peace and prosperity in the post-war world. He also should be clear-eyed about who are America’s real friends and who are just playing to his vanity.