I feel like I'm missing some nuance, because it looks like it's basically just taking the largest population cities in the US and drawing circles around the ones near each other. "Most economic activity happens where the most people live" doesn't seem like a particularly novel insight.
The claim, as I understand it, is that commerce within a megaregion is more tightly integrated than commerce between megaregions. If this is the case, there should be more trade between Baltimore and Boston than Baltimore and Raleigh (controlling for population/GDP/infrastructure, I suppose, and therein lies the rub), despite the fact the latter pair is closer.
I don't really agree. First, having lived in a few of those "megaregions", I really agree with the author that they each have distinct and unique characters. I also see other nitpicks in some comments here about "there is a lot of wide-open spaces in those circles!" - that seems a bit silly to me given that many of those circles include wide expanses of ocean, and it seems clear to me that the author just means to highlight the related urban areas, not the emptiness in between.
But more to your point, there are plenty of other sizable cities that are not part of the megaregions the author highlights, and I would agree that those cities are less dynamic and less engines of economic growth due to their isolation - places like Phoenix, Salt Lake City, Minneapolis, etc. The only difference I think is that it "feels" to me like there is an emerging megaregion on the eastern slope of the Front Range in Colorado, i.e. Ft. Collins-Boulder-Denver-Colorado Springs area.
The real insight (which isn't much) is that people tend to do business with those who are closer to them. It isn't a surprise that if I need something at work now my boss might send me to the local war-mart or whatever.
However that someone in Dallas is more likely to choose a supplier in Austin than one in Boston is interesting - once you leave Dallas does the extra distance to Boston mean anything? I can come up with all kinds of weird ideas.
Yeah I question the usefulness of the concept if stretched too thin. It has Chicago and Pittsburgh in the same megaregion and yet I don’t think those two places interact much at all. I can buy SoCal, the Bay Area, and Boston-DC as megaregions though.
I have a minor nitpick with the shapes. There is a lot of wide-open nothingness under these "mega" region shapes. Washington DC to Boston should be more of a long rectangle, as the rest of upstate PA and NY are basically empty woods. Most of the region south of Orlando are mangroves and swamp. The NorCal one should be a line from SF to San Jose. Although Sacramento is growing, it's quite distinct from the bay area, and there is a lot of nothingness between the two. And these are just the places I've lived and are familiar with. Wouldn't surprise me if the rest of that map is similar.
