Umm ... the Sierra Nevada, the Olympics, Cascades, ranges all under water? Most of the Great Basin is over 5000 to 6000 feet in elevation. The vast majority of the west would not be underwater. Even if someone tried to argue that there was some sort of tectonic force at work or whatever that much activity would essentially "end" life on the planet in order to put those areas underwater. Texas and Florida make sense most of the west does not. This map is cool but it is not based on anything scientific.