We discovered through experience that the more complex a system, the more difficult it is to force that system to collapse. We found this when we attacked the economies of Germany and Japan in the second world war, and I rediscover it every time I try to get the weeds out of my yard-- there is just too much going on to have what I can call a decisive victory with the tools I have available.
Our economy is much the same way. The alarmist debt clock demonstrates this well. The numbers our country faces are enormous, and pose a huge investment in many parts of our daily lives. Pundits often look to the debt as some kind of 'gotcha' with policy, telling us that as the number grows so too does our impending doom. But the clock also shows a hugely complex system, one that should have fallen apart by now if it were truly in danger of such an epic collapse.
Our economy, and by extension our debt, is one of the greatest assets we have for our national defense. Our ability to raise capitol quickly and apply our expertise grants us advantages in traditional and non-traditional means of conflict that many of our adversaries cannot hope to match.
I fall into the camp that believes too much debt is a bad thing. That being said, my personal budget us much more simple, and therefore much more easily disrupted and destroyed, than the national resources. I think we could manage our funds better, but when it comes to national defense, I don't think our military spending is nearly the cause for concern that others would point it out to be.