Americans, on American soil, are killed by terrorists at the same rate as they are killed by sharks, and most Americans live nowhere near the sea. Spending billions of dollars to blow up a couple of dozen men in a cave, thousands of miles from our shore, is a complete waste of resources.
Fundamentally, you can fight terrorism by moving away from oil. Terrorist organizations are, effectively, the end-result of poor government. And they serve as useful idiots for local governments to screw over their neighbors, so they dump oil funds into these groups, who then go out and commit horrible acts locally (there are many terrorist attacks every year, just not in America). Spend the same amount of money that we spend blowing up ordnance in the Middle East on subsidizing fuel from Scandinavia and South America, loosen restrictions on fracking, and Middle Eastern terrorism will start spinning around the drain.
Rather than blowing up terrorists in the hills, there would be far more value investing in and protecting schools and infrastructure in countries like Afghanistan and Iraq. But that’s only really feasible if you’re willing to occupy and own these countries for a generation or two, and hand-recruit the government and military by American control, to weed out corruption and sectarianism. That’s something that Bush I realized was necessary for any real change, but beyond political viability. His son was too stupid to realize this was the solution after actually going through the effort of occupying Iraq. He squandered the opportunity instead on establishing American bases, to fight terrorism and protect Middle Eastern oil, and left it to the Iraqis to try and figure out how to become a functioning nation again.
But in terms of saving American lives, you would do a thousand-fold more investing in self-driving cars, to bring down vehicle-related deaths, or setting up a million dollar X-Prize to invent an alcohol replacement that was still fun, but didn’t make people so unsafe in a vehicle or to their romantic partner and society. In terms of return on investment, you’re just not going to beat that, even if you can figure out how to kill terrorists for a penny each. And certainly not when you’re spending billions per one.
Personally, I think that there is a great value in moving nations towards modernity. Global stability is a boon to business and trade, and functioning states with a free market are much better investments than backwater dictatorships, even if the former is going to slowly raise their prices over time. And military intervention is, probably, a necessary and cost-effective method towards that aim. But fighting the disaffected rebels of those dictatorial nations is not, in most cases, going to be a particular meaningful use of resources in that aim. It’s like wiping sweat off a sick man’s brow and claiming that you’re helping to cure the world of the flu. You’re not even rising to the level of fighting a symptom of the illness. You’re just clearing away the evidence of that symptom.
A good solution would probably be something along the lines of strong-arming dictators into benevolent activities towards their people, rewarding them if they do so, and taking them out if they do not. Probably you would need to sell China into supporting this (or Russia, but that’s not going to happen), and then patiently and consistently enact this strategy for decades across many presidencies.
Unfortunately, we have not had a President smart enough and bold enough to move along those lines since Bush I, and I’m not hopeful that we’ll see another such President for quite some time. Intelligence is not appetizing to the party that encourages boldness, and boldness is not appetizing to the party that encourages intelligence.