American democracy is tottering. It’s not clear Americans care.

During the opening speech at Thursday’s Summit for Democracy, President Joe Biden told the assembled international leaders that the stakes of their meeting were nothing less than existential: that the survival of democracy itself depended on what his audience did next.

“We stand at an inflection point in our history,” Biden said. “The choices we make at this moment are going to fundamentally determine the direction our world is going to take in the coming decades.”

No one other than Secretary of State Antony Blinken was in the room to hear...