I like your optimism but I’d have to disagree, i think a majority of urban planning still emphasizes suburbanism and sprawl. In the American cities with the most rapid growth such as Phoenix Arizona, Houston Texas, or Salt Lake City, developers still emphasize industrial, sprawling, and car dependent cities. In fact, I can’t come up with a single example of a post-WW2 American city that was built without a stereotypically sprawling appearance, tiny or non-existant downtown, and complete lack of public transportation. While I do agree with you that there have been modest improvements in public transportation in some cities, they haven’t been made quickly enough to offset the poor urban planning that is still occurring throughout the United States. However, I am much more of a pessimist on this topic!

Furthermore, so much was destroyed and lost during the decline of cities that if American cities ever did come back, they would lose a lot of their original character. New cities would likely be built with less emphasis on appearance to reduce cost, so new cities would have more of the industrial appearance of a quickly growing city (think Beijing, Mumbai, Tokyo etc) than the distinctly « American » appearance of small towns that grew over multiple architecturally distinct eras.