For the nuclear deterrent, the worst-case scenario was basically the end of the world as we know it. Either the USSR takes over the world, or global civilization is entirely wrecked. I'm not sure which one would have been considered worse. Either way, hundreds of millions, perhaps billions, die.

For counter-terrorism operations, the worst-case scenario is orders of magnitude smaller. There appears to be no credible threat of any terrorists obtaining WMD, so they're pretty much limited to casualties in the thousands.

I think that much of our current woes come down to applying cold-war thinking to terrorism. The situations just aren't comparable. We were facing a true existential threat from a powerful enemy that outclassed us in many ways. Now, we're facing a minuscule threat that can, at most, kill a small number of our citizens from time to time. There were realistic scenarios that end with, "and the US was destroyed/defeated by the USSR", but there are none that end with, "and the US was destroyed/defeated by al Qaeda".