You can't rely on Stanislav Petrov
Those of us who survived the cold war had it drummed into us that each side had a network of satellites watching each others' launch sites, and at the first sign of a missile heading into the air on a ballistic trajectory the other side would launch all their nuclear arsenal. After all, they can't wait for the nuke to land on one of their launch sites.
It's not clear whether this doctrine of mutually assured destruction is still in place between Russia and the US, but do you want to take that chance? It probably is still in place between India and Pakistan, both of which have ICBMs and a nasty border dispute in Kashmir.
You nuke a terrorist camp in Pakistan, the Pakistani missiles launch, and the Indian ones launch in response. Billion dead overnight. Well done, guys. The worst case is of course the destruction of every Russian, Chinese, American, British, and French city of over 1 million population. I think that's now somewhere above 2 billion people.
The definitive film on this is of course Dr. Strangelove. Stanislav Petrov I mentioned above is the Russian officer who chose to violate orders and not launch when his instruments (wrongly) told him to, thereby not starting World War 3.
(You might be able to avoid this by briefing the relevant countries in advance, and hoping that they don't leak it to the terrorists or go public with it to point out that the US has been taken over by a madman)
'Terrorists' live in cities
This is why "zero immediate collateral damage against innocent civilians in these strikes" is so completely unrealistic. It assumes you have a group of 'terrorists', and only terrorists with no staff or wives, living out several miles from anywhere, not even the local convenience store.
Bin Laden was living "0.8 miles (1.3 km) southwest of the Pakistan Military Academy in Bilal Town, Abbottabad, Pakistan, a suburb housing many retired military officers". Abbottabad is a city of 1.4m people.
ISIS are mostly operating from cities in Syria. Because they need food and fuel like everyone else.
It's not entirely clear whether it is directly against international law to use "weapons of mass destruction", but you can bet that people are going to start arguing that it is. You will effectively have made it politically impossible for any other country, especially in Europe, to continue collaborating with the US in the "War On Terror".
Even if you don't trigger an immediate nuclear exchange, Russia and China will certainly now have to build up their nuclear arsenals to the point where they can effectively retaliate.