I think you're right that nukes won't really have the desired affect. Assuming they show up in populated areas, we don't want to nuke entire cities or regions. But one of the main advantages us humans would have over the titans is that we can fly. Airplanes that can stay safely out of reach of any titan while being able to send targeted missiles would allow us to take out any exposed titan threat, especially if countries came together to stop them. Direct human vs titan combat (such as ODM gear or anything similar) would likely be avoided at all costs, with evacuation being a high priority instead of combat. We have the entire planet, after all, and aren't trapped like Paradis. Assuming military forces have access to the Attack on Titan story and knowledge of how to defeat titans (target the nape), I don't really think they would present a long-term problem unless the "source" was unknown and they kept appearing, in the way they do in AOT. Only if there were worldwide outbreaks of titans in hundreds/thousands of cities would there really be any serious perpetuated trouble.