Rep. Alexandria Ocasio-Cortez and her “Squad” seem to think their criticisms prove their love of country. But even the most fervent patriots allow for improvement. Progressives might be more convincing if they were more evenhanded—spending some time extolling America’s virtues rather than hammering away at its shortcomings. Populists have grown frustrated with liberal celebrities, journalists and politicians they see as insufficiently thankful for the opportunities America has provided them—one reason Mr. Trump’s defense of the American flag and condemnation of Colin Kaepernick’s refusal to stand for the national anthem have resonated with these voters.

Populist patriots are equally disappointed with the results of decades of Republican economic orthodoxy. Freely flowing American capital builds factories around the globe, raising many people’s quality of life. But this arrangement fails to deliver clear benefits to America’s working class. These voters went along with lower taxes, free trade and other conservative economic positions because they believed, for a time, that these policies would generate more jobs for Americans.

Eventually many Americans saw enough real-world evidence to doubt that economic vision.