Soldiers are expendable.
Ultimately yes, but you don't want to expend them for just any old thing. Certainly not in that trash heap of a country. We should have finished that job, and it was job that needed doing, about 5 or 6 years ago. It took us less than 5 years to defeat Nazi German and Imperial Japan, and assorted hangers on. We could have defeated these people too. IF we were willing to pay for it, in terms of a significantly increased military, in both numbers and money. We weren't and we aren't. So we die the death of a million cuts instead. Successful war cannot be made on the cheap.
Or we could have just nuked the place and taken our lumps in 'world opinion'. World Opinion isn't worth a single soldier, airman, sailor or Marine's life. Not one.