BRUSSELS — President Donald Trump’s threat to impose a trade embargo on Spain has delivered yet another jolt to the European Union, forcing European leaders to rally around Madrid. Trump launched his broadside on Tuesday after Madrid declined to allow U.S. warplanes to use its air bases to attack Iran. Prime Minister Pedro Sánchez stood firm on Wednesday , describing the five-day-old war launched by the U.S. and Israel on Iran as illegal. French President Emmanuel Macron rushed to Sánchez’s