Generally speaking, I think it makes more sense to make your enemy respond to your maneuvers rather than to find yourself constantly responding to his maneuvers. If you find yourself responding to his attacks the principles of battle probably aren’t in your favor i.e surprise, initiative, offensive, mass and synchronicity of force, maneuver, objective, etc. That being the case, perhaps rushing off into a major war in response to a few missiles that impacted without significant effect isn’t the wisest approach here.
So if Mexico launches a few missiles at Los Angeles and Houston every day for ten years, we should just take it? I mean common, a war over a few missiles? They only killed a few civilians anyway, why not just wait it out and see if they run out of missiles?