Though most of the world became uninhabitable without air & water filters, the newly flooded areas of the Southeast US became so densely forested that they remained viable. This region is now largely composed of thriving wetlands, and is known as Bayou Reach (from Creole *Bayou Riche*).
The rapid erosion created by the new waterways resulted in substantial sedimentary deposition, leaving most the new mouths a system of deltas & braided streams. All on the map are still wide enough for maritime traffic.