The U.S. can’t be protectionist and world leader

President Joe Biden likes to call the United States “the indispensable nation.” By that he means that America is the only power simultaneously mighty and benevolent enough to preserve whatever is left of a liberal order — one in which rules and multilateral institutions govern, among other things, a system of relatively free international finance and trade.

But what if the U.S. itself, even under Biden, turns against the system it’s supposed to guard, becoming an agent of economic nationalism, international fragmentation and hostile bloc-building?

Doubts to that effect have popped up throughout the Pax Americana, the long period of U.S. leadership that followed World War II. What most frightened America’s friends abroad, though, was Donald Trump in the White House. His “America First” worldview was a throwback to a much earlier U.S. stance of isolationism and nationalism.

The infamous symbol of that older tradition was the Smoot-Hawley Tariff Act of 1930. Named after its…