Florida is gone. The Sunshine State becomes the Pirate State, as the Keys advance north to the Georgia border. Flooded Florida, already a haven to the financially and morally corrupt succumbs to total pirate lawlessness as America abandons the remaining dots of land slowly sinking from sight.
Texas is gone. After decades of corrupt privatization of infrastructure, Texas is left defenseless against vicious hurricanes to the south and advancing heat domes to the west. The gun culture takes over, turning the state back to the 19th Century of outlaws and gunslingers. Only this time, the frontier features automatic weapons.
Nevada is gone. Death Valley tops 160 degrees one summer, and the next summer Las Vegas follows suit. Roads melt. The air-conditioned culture collapses, as both water and electricity fail, and once-bustling casinos crumble when I-beams melt.
Southern California is gone. As the Colorado River runs dry, and the oceans rise, the state becomes uninhabitable when raging wildfires sweep away whole towns in minutes.
The Northeast and the Midwest become overwhelmed with climate refugees, but it quickly becomes apparent there is no escaping the climate crisis. The great coastal cities are swamped, massive storms crack the skies, millions of people fill camps that breed plagues, as food rots in farmland already stripped bare by corporations who used toxic chemicals in a relentless chase for more profit.
The Green New Deal is too little, too late, the Paris Accord too meek. Mass extinction of the human race begins. The year is 2022.