ICBM is likely to deliver a nuke. Which will probably take out a 20 km radius circular area. It is not going to be used to target a base with 100 soldiers.

It is if the goal is to deter without launching a city roast fest. That’s one possible step to e.g. answer a first limited strike without starting a disastrous exchange. And US nukes can be set to low yield.

If NATO ever has any intention of deterrence through detonating a nuke, it will be done in exactly the way it's been specifically planned and openly explained: France has a specific nuclear policy, one of the only ones, that allows them to use nukes before an adversary does. They have a specific nuclear missile fired by plane that will be used as essentially a giant warning shot.

Nobody would fire a warning shot using an ICBM, because if things are hot enough to require a warning shot, that leaves a whole lot of interpretation up to your adversary who is quite likely to respond with their own ICBMs, before finding out yours were loaded with conventional munitions to make a point.

There are however, shorter range ballistic missiles, Russia has a lot of them (the US mostly gave up mid range ballistic missiles in a nuclear treaty) and has even launched a few with concrete "nuclear warhead simulation masses" at Ukraine.

Or a dozen nukes.