Larry Jacobs, a political science professor at the University of Minnesota’s Humphrey School of Public Affairs, said that Trump’s behavior has generated confusion about what the country’s positions are.

“Ronald Reagan was very clear, there’s no ambiguity about his views about the world and his willingness to pursue them. None,” he said. “Sometimes he was criticized . . . but there was a clarity and a consistency and a pattern that was established.”

With Trump, in contrast, “both our allies and our enemies are at a loss to understand what the president means,” he said…

“Trump’s threats work to some extent against weak targets, but not against stronger ones. Canada and Mexico, which are so dependent on exports to the U.S., have been willing to make tough concessions rather than risk serious harm to their own economies. Korea, which is so dependent on the U.S. security umbrella, was also willing to do a quick deal,” said Edward Alden, an economics professor at Western Washington University. “But bigger trading partners — China, the E.U., even Japan — have proved far less compliant.”