Really, we’re humans and can adapt, though. How much of the Netherlands ought be under water? Maybe a dike the size of the North American coast would be expensive to a short term thinker, but think of the massive benefits of not drowning the nation. Plus it’d be a pretty good public works project, I imagine. 
Sure we’ll “adapt.” Humans will survive. But the process of adapting will be enormously disruptive. Tremendous amounts of money will have to be spent either to move populations or to prevent flooding in susceptible areas - money that could have gone to other purposes.
As to a dike around the North American coast, think of the enormous disaster if a breach developed. How high do you think you’ld have to make a dike around Florida to survive a hurricane-driven tidal surge? An accident would make the Mississippi floods of a few years ago, when the levees were breached, look like nothing.