What The US Would Look Like As Mega-Regions Instead Of States
America 2050 project proposes that we begin to view the country's urban areas not as discrete metropolitan areas but as interconnected "megaregions." Megaregions are areas where large cities and the spaces in between share "interlocking economic systems, shared natural resources and ecosystems, and common transportation systems."
They identify 11 in the U.S. — Cascadia, Northern and Southern California, the Arizona Sun Corridor, the Front Range, the Texas Triangle, the Gulf Coast, the Great Lakes, the Northeast, Piedmont Atlantic, and Florida (it's kind of dangling off on its own there, anyhow).
In other words, these are the areas in which residents and policymakers are the most likely to have shared common interests and policy goals and would benefit most from co-operation with each other. It's especially important, because as the Regional Plan Association notes, "Our competitors in Asia and Europe are creating Global Integration Zones by linking specialized economic functions across vast geographic areas and national boundaries with high-speed rail and separated goods movement systems."