“Why does he hate us?” is the question American foreign-policy types often hear from European friends and colleagues when the subject of Donald Trump comes up—as it often does. With Mr. Trump and Secretary of State Mike Pompeo in Europe this week, it seems an auspicious time to attempt an answer.

The news isn’t all bad. When Mr. Trump and senior administration officials talk about China, they attack it for abusing the international system in a ruthless quest for global hegemony. Their reading of Europe is different: that...