President Trump has squabbled with his European counterparts over Iran since he left the 2015 nuclear deal. But the tactical disagreements have obscured how much Berlin, Paris and London agree with Washington about the Iranian threat. Now Tehran’s attack on the global oil supply finally has moved Europe toward the Trump position.

That’s the meaning of a joint statement Monday evening by German Chancellor Angela Merkel, U.K. Prime Minister Boris Johnson, and French President Emmanuel Macron blaming Tehran for the Sept. 14 attack...