An article from last February in APSR, of which I've read only the abstract, concludes, based on an "original survey experiment," that the U.S. public "has only a weak aversion to using nuclear weapons and that this aversion has few characteristics of an 'unthinkable' behavior or taboo."
The cite is: Press, Sagan & Valentino, "Atomic Aversion: Experimental Evidence on Taboos, Traditions, and the Non-Use of Nuclear Weapons," Am. Pol. Sci. Rev. 107:1 (Feb. 2013):188-206.
What to make of this? Hard to know without having read the article, but one (elitist) inference might be that this is further evidence of the U.S. public's backwardness (for lack of a better word) when it comes to security issues.