Not every nuke needs to be a city destroyer. You could use tactical nukes instead of tanks and mass infantry for example. Maybe you have a few elite squads on the ground who basically just serve to mark targets for orbital ICBMs to quickly destroy. Wars would be over by the time the ICBMs are launched. You could identify key industrial sites in advance of the war and basically blow up any capability for a follow up response or armament buildup as soon as war were declared. With enough ICBMs you could overwhelm air defenses; maybe with a swarm approach you could get away with a lot of decoys that are just made of cheap inert material versus the air defenses that have to assume each decoy is active. People think an ICBM only army would just be a huge hammer, but really it would be best used like a robotic surgical scalpel.

I know you're not necessarily advocating for this strategy and just sharing that they're much more advanced / tactical weapons now, but this strikes me as too cavalier.

It might be true that we can create nukes which have minimal fallout and minimum impact area (I have no idea to be honest), but this ignores the broader consequences such a strategy would bring. Namely that you remove the taboo of using nukes and start to normalize it. It then becomes more justifiable for other countries to also use nuclear weapons, at which point escalation becomes ever more likely. Imagine the consequences if Russia were to use nuclear weapons in its war in Ukraine. Frankly we need as large a stigma as humanly possible on the use of these weapons.

What would even be the consequences if Russia were to use nuclear weapons in Ukraine? Maybe a lot, or maybe absolutely none depending how they are used. If they are used in a Nagasaki capacity then yeah, that would lead to repercussions, but you can do that with conventional arms too. See what the allies did to Dresden for instance, or the firebombing of Tokyo. The issue is not the weaponry, but the act of threatening civilians versus strictly military targets. If Russia used nuclear weaponry as they currently use their conventional missile weaponry in ukraine I'm not sure the international community would care more than they currently care about the war, in a world where the political taboo of using nukes did not exist.

With hindsight, either of those look like better options than what we ended up doing (20 years, 2 trillion dollars, nothing to show for it).

I agree the outcome of the wars in Afghanistan and Iraq could have been better. In fact I would even agree they were disastrous. But:

If we had nuked Afghanistan we (probably) would have kicked off WWIII.

If we had done nothing further attacks may have occurred.

Both of those seem at least worse than what actually happened.

imo, there's no possible world where not invading Afghanistan causes 2 trillion dollars of attacks. (especially because 9/11 had only very weak links to Afghanistan)