Humans will survive like cockroaches.
However, like the Roman Empire, the existing/U.S. civilization will end because it is too easy to survive in current civilization. Fewer people will get involved. Fewer people will feel that the U.S. is something to be proud of and part of.
So, entitlements will grow (hey, can anyone say Obamacare) and politicians will continue to bribe the ignorant population with their own money until the economy collapses.
No original thinking on my part.