Do global north or so-called "first world" countries who aren't in or near a theatre of warfare have air/missile defenses at the ready?

I'm aware that the best defense is the threat of total annihilation to any country or group that shoots a missile at north America.

Consequences and strategic viability aside, what would happen if one, two, or a true promise number of missiles were launched at Ottawa? Is it that they would need to take an orbital trajectory and as such would be defended by similarly launched defenses?

What about the UK? Are there THAAD batteries dotting the perimiter of london just hidden?

Or is it just one of those fun illusions of safety that could be broken by a sufficiently determined group?

I (probably obviously) don't know anything about the military beyond stuff posted in the news mega