Most likely redditors being lazy and retarded to do their own original research, to be fair there have been significant chunks of cities that were demonstrably demolished to make room for expansion of vehicular infrastructure. For instance, I whipped this one up using GIS/paint. This is an archival aerial photo of Detroit I combined with its current highway layout (red) and dedicated surface parking within the Loop (orange)
However just looking at an aerial image from the 40s/50s doesn't really do what's changed in these cities that much justice, continuing with Detroit in the modern day, the real reason why the city looks so empty is not just due to the highways, but almost entirely due to its overall infrastructural decline that many similar US city have also suffered from, both in quality and livability, to the point that many of these structures you see in older aerial photos got abandoned and demolished and were never replaced (or just filled in with surface parking lots as a cheap way to reuse old space). It's quite unfortunate since they lose out on a lot of uniquely American pieces of architecture but is expected as many of these places brought their decline on themselves through policies that incentivized deindustrializing domestically and failing to adapt multi modal infrastructure for the needs of an ever evolving country.
There's no denying that buildings were demolished but these look to be the same SFH stock that literally has rotted away in the rest of the city (diagonal cutting, rather than building along main avenues, preserves most of the commercial businesses--Detroit is definitely zoned have the commercial businesses cluster around the main corridors).
But then again, Europe has dedicated an enormous amount of space to rail infrastructure, and the hand-waving of "it's rail, so it's okay" doesn't make sense if you're crying about "destroying the city". I'm not judging Europe for doing so, likely those too were crummy buildings on the way out.
There were a few corridors (including Detroit, but other cities as well) where the highway was built over a main thoroughfare (which is bad not only for the commercial district but messes up traffic flow) but for the most part they weren't. Furthermore, the inner-city freeways were usually the ones to be built last because the Interstate Highway System was designed to be an inter-city system, not an intra-city one. City leaders often demanded the downtown area be a hub system but by that time the downtowns were in decline anyway. (Related; all these "before and after highways" could just as easily be "before and after Civil Rights Act").
The reason I am so suspicious of this is even when it comes to freeway widening plans--why spend millions on a highway widening when you can spend billions on a train system that goes nowhere--is that they still play the same cards about destroying communities and businesses. But many of these plans (including Katy Freeway's widening) online and the truth is less dramatic. In addition to much, much better resolution so you can see what exactly went away, what actually gets torn down isn't much to write home about...gas stations, fast food, and the occasional 3-story office building. Single-family homes as well, but urbanists would rather knock these down anyway.
That is of course, the other thing, urbanists don't actually
care about the structures knocked down, it's for the wrong thing. They'd cry about homes being bulldozed for a new highway widening but would happily run them down at any time if it was for a rail line. They'd cry about the street grid being damaged by a freeway but would happily close off any street if it suited them.
