I still don't think I understand what people talk about when they say the world will start to flood. From what I've seen, if all of the polar ice caps melted at once we'd see the sea level rise maybe two feet.
Now, I don't know about the rest of the world, but in Florida pretty much everything is higher than that. You go to a beach and you walk maybe 4-6 feet downhill to get to the water. An increase in the sea level of two feet would make for smaller beaches, but I fail to see how it would sink half of North America. Even if it could, it would be very, very shallow.