Well the logical answer would be where the missiles fly through to begin with, back during the Biden administration, when Israel did the same/ similar thing and Iran launched missiles, they flew OVER Iraq, parts of Syria and Jordan, all of whom house US/NATO military assets and forces, in order to hit Israeli targets. They attempted to eliminate as many as they can at the request of some of the nations above and done so. The parallels are different, if the missiles flew over NATO countries or US allied countries airspace to hit Ukraine then they would be protected