One of the chauvinistic, self-glorifying myths of American liberalism is that the US has especially strong institutions. In this story, trotted out occasionally since 2016 to reassure those who are worried about Donald Trump’s influence, the private and public bodies of American commerce, governance, healthcare and education are possessed of uncommonly robust internal accountability mechanisms, rock-hard rectitude, and a coolly rational self-interest. Trump can only do so much damage to America’s economy, culture and way of life, it was reasoned, because these institutions would not bend to his will. They would resist him; they would check his excesses. When forced...