(I know a lot of Americans are sceptical about global warming, and I'm not meaning to start that debate; just treat it as another "what if" scenario that some of us think isn't totally outlandish.)
I don't want to start a global warming debate either, to me its mostly just another scenario we're either prepared for or not - but I agree, the US is a bit behind in preparing for climate change. I recently ran across this article which at least indicates that emergency management folks are starting to consider the ramifications of climate change - http://homelandsecuritynewswire.com/rise-sea-levels-threatens-california-ports-infrastructure?page=0,0. (If the URL doesn't resolve for you just connect to the homelandsecurity.com website and search for the Dec 15 article "Rise in sea levels threatens California ports, infrastructure.")