By far the biggest problem is going to be the durability of the withers, which is town level. Nuclear weapons would be the easiest way to get rid of them, but humans are hesitant to use them as is, which would be especially true for countries that are allied to norway. Though as far as i remember, withers don't travel very far and they're also pretty slow in terms of travel speed, so keeping track of them and organising a coordinated response will be easier if they're all in the same general location for a long while.
The withers also don't exactly have the range or attack speed to hit most modern aircraft, so it might be possible to chip away at them with enough carpet bombing, strafing, and artillery, considering norway and it's surrounding countries are pretty well-equipped to handle a lot of international forces, since they're all a part of NATO and will have build plenty of facilities to support them and know how to work together. But if the starting location is remote enough i think humans might seriously consider using a nuke or two if they get really desperate and evacuate people, which is definitely the best wincon.
Either way, the withers are going to take a loooooooong time to seriously cripple humanity, especially if they spread out a lot, so they have plenty of time to figure out how to deal with them. I'll see what others think before i vote tho
