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.
