President Donald Trump shocked world leaders last week by doing nothing more than living up to the promises that got him elected in the first place. Trump, who campaigned on a platform of economic nationalism that even many in the Republican Party have been keen to paper over and ignore, said that he was going to pass new tariffs on steel and aluminum as a measure to protect American steelworkers from undue overseas competition. The proposal was met with scorn by many of our allies, including European Union leaders who thought this would be a good time to step up to the microphone and “get tough” with the United States.

Um. Bad idea, guys.

“So now we will also impose import tariffs,” said European Commission president Jean-Claude Juncker at an even in Hamburg. “This is basically a stupid process, the fact that we have to do this. But we have to do it. We will now impose tariffs on motorcycles, Harley-Davidson, on blue jeans, Levis, on bourbon. We can also do stupid. We also have to be this stupid.”

He said this, of course, in such a way that disguises the fact that the U.S. is already facing massive trade imbalances with the EU and other international allies. But Trump quickly responded, telling the EU leader on Twitter that two could play at that game.

“If the EU wants to further increase their already massive tariffs and barriers on U.S. companies doing business there, we will simply apply a tax on their cars which freely pour into the U.S.,” he wrote. “They make it impossible for our cars (and more) to sell there. Big trade imbalance!”

To be sure, Trump has faced criticism over the tariffs from within his own party, but one of his top economic advisers, Peter Navarro, told CNN that it was nothing the president was inclined to get worked up about.

“All 16 of those candidates didn’t agree with his policies, either,” Navarro said on CNN. “They’re dead wrong on the economics; there’s no downstream effect here. There’s only a president saving and defending our aluminum and steel industries.”

Navarro went on to say that it would be difficult, if not impossible, for the U.S. to negotiate exemptions for close national security allies without overhauling specific trade agreements.

“As soon as he starts exempting countries, he has to raise the tariff on everybody else,” Navarro told Fox’s Chris Wallace. “As soon as he exempts one country, his phone starts ringing with the heads of state of other countries.”

Trump promised “America First” and with this policy, he aims to live up to that mantra. Not all of our allies are going to be thrilled with the results, but hey, we didn’t elect Trump to make the European Union happy.