A (modern) ballistic missile is basically a rocket carrying a few nuclear warhead to space and then falling from space back to earth, and very high speed while splitting the warhead on the way down to hit several targets (while some of these warhead may-be dummy). And this let alone all the fancy hypersonic ballistic missile which are steered by "bouncing atop the upper atmosphere* making them less predictible while travelling even faster.
So basically, we won’t know the exact target before the last moments of the flight, letting may-be a few minutes to the inhabitant to hide.

Regarding “anti missile defence” I assume that the people who knows the details won’t post about-it on lemmy. What you need to remember is that even if you catch 80% of the missile falling (let’s be optimistic), it will still do a lot of damage.
To take French arsenal, according to Wikipedia, a Triomphant class submarine can carry 16 M51 ballistic missile, each of them carrying 6 warhead. A submarine emptying it’s whole load on a hostile country would shoot like 100 warheads. Assuming that air-defence can intercept 80% of them, it’s 20 nuke exploding. I can’t think about any country which would resist to getting 20 cities wiped out of the map.

So yes, if nukes start to fly, we’re fucked up.