If President Trump follows through on his threat to impose tariffs on steel imports, expect to see an immediate response from the European Union — including retaliatory tariffs on, of all things, bourbon.

This may seem an oddly disproportionate choice. Everyone needs steel; bourbon, on the other hand, is just a hipster fad and a good-ole-boy mainstay, right?

In fact, a punitive tariff on bourbon and other American whiskeys would be both a symbolic and a substantive body blow — a strike at a unique American product that is enormously popular overseas. Should the tariff dominoes fall, it will be a case study in the shortsightedness of a supposedly “America first” trade policy that, in the end, hurts Americans the most.

Mr. Trump’s intention to pursue better trade deals for the American people is laudable, and done right it could add jobs to some of America’s long-suffering industries. But very few industries are truly domestic, with no interests abroad, and when free trade suffers, they suffer, too.