Trump mistakenly thinks that America, thanks to its thuggery, is more powerful than ever.
Trump was becoming increasingly focused on Iran and, to a lesser extent, Venezuela. He launched a ruinous trade war against China and threatened Europe with the same. There was simply no time for his good buddy Kim.
If another president was running the U.S., that question would be easy to answer. Europe shares its fundamental values and economic order with the United States, not with China, an authoritarian country.
Threatening free, peaceful navigation is a very serious matter that should have consequences for the theocratic dictatorship in Tehran.