
The only thing you'll need to be careful of is that one nuke will destroy all the structures in a state, so if your troops are reliant on the infrastructure to get supplied. Nuke a state to cripple supply lines by destroying ports and infrastructures.
If you want to cripple the enemy's air power in the region, nuking the province with an airbase in it will destroy 99% of the planes stationed there. Strategically, nukes wreck all structures in the whole state. That said, on a large front a nuke will probably only hit 2-5 enemy divisions. A nuke will completely obliterate organization and take a very large chunk out of any divisions hit by them. With all this in mind, what are nukes good for? Tactically, I use them for breaking through chokepoints or establishing a beachhead. Strategic bombing is probably the better long term answer. War support only affects surrender process significantly when it's <30%, and you probably won't get them that low with nukes alone. If you're fighting a war of attrition against a large country, their manpower trickle should be higher than their casualty rates unless you grossly outgear them already and are just slaughtering their forces, in which case why worry about war support? War support largely affects mobilization speed when harsher conscription laws are increased and command power increase, both of which are not going to really make or break a war with the AI.

Most countries in the lategame have high war support, perhaps even overflowing to above 100% so you're going to need to nuke a lot to make a dent, and nukes have diminishing returns on the war support hit. Nukes can lower war support by a large %, as high as 10% if you nuke a major city or capitol.
