[GunboatDiplomat]

Yes, but that's different than that being a scenario which is remotely feasible (it's not). Not renouncing a first strike during the Cold War was a measure to counter massive Soviet conventional numerical advantages in the European theater. France also does not guarantee no first use, because it wanted the Russians to know that crossing into France would necessarily mean nuclear retaliation on their cities (as if the Russians made it to the French border, the conventional war would essentially be lost for NATO).

In short, there are no realistic circumstances under which the US would launch a first strike with nuclear weapons. The political cost is too high, and the benefits could never outweigh the costs.