@Gunfighter:
A) Terrorists are covert. It's like trying to hunt for a needle in a haystack. Sure it hurts when it pricks you, but you have to do a *lot* of work to find the needle in the haystack, using the conventional method of search-and-destroy. I would argue that spending a fraction of money on better intelligence would be better (e.g. buy a metal detector for the haystack). US intelligence officials had gotten wind of a airplane hijack scheme before 9-11 occurred, but they dismissed it and the towers fell. Bin Laden was not defeated in a siege. He was caught by US intelligence, then Obama sent the SEALs. You don't need to have an army worthy of 2 full-scale wars to support a commando unit.
B) The fact that the US spends 26% of government spending on the military doesn't make it a constructively used 26%. The Soviets had workers dig holes and fill them in to artificially boost GDP and employment - that definitely worked, except it was not constructive. How is building machines designed to get destroyed intentionally more constructive than getting sick people better or better preparing the next generation?
C) And why is Canada not expecting a (conventional) attack soon? Because...it isn't worth it to go across an ocean to attack it by force? Same for the US. As I said, terrorist attacks are covert, and a large army is not necessarily going to defeat them, especially *before* the attack occurs which is when you want to stop them.
D) I will concede that the US Government is really inefficient at health and education, and that it is more efficient at maintaining an army. Doesn't mean that it should therefore take money from health and education and put it in defence. You don't do something because it's efficient, you do something because it's useful. A case could be made for the government spending less on the whole, and leaving health and education to the private sector (and of course taxing less so people could purchase the services from companies instead). e.g. The US needs $400m in defence, $400m in health, and $400m in education, but since the government sucks at providing the $800m worth of health and education it should just stick to spending $400m in defence and not spend any on health or education. There is no case to be made for spending $1200 on defence because hey that $800m in health and education isn't working, so let's spend that on even more defence instead.