America’s cities (metropolitan areas) changed radically since the dawn of World War II. At that point, cities were dominated by their core municipalities (central cities), around which people traveled much greater percentages by transit and lived in much higher densities. Automobile oriented suburbanization had increased rapidly in the 1920s, but was slowed by the economic upheavals of the 1930s.
The doubtful claim that low density US cities impose a cost to the economy of $400 billion is countered by their being the most affluent in the world. Nine of the top 10 cities in GDP per capita are in the US and more than 70% of the top 50. The highest GDP per capita city in the world is one of the least compact, Hartford, with an urban population density among the bottom 10 out of more the than 900 urban areas larger than 500,000 (See here and here).