(Said in the Spirit of Christmas:) Arguably, they understood it well enough to not have tested it.
Perhaps further, they understood they would have to gain a stronger foothold within America, which it appears they now have obtained.
It is doubtful our CIC would push the button before it was too late, if at all (and, his family would no doubt be on a hurriedly arranged trip out of the country).
If you are referring to the situation right now, I think MAD doctrine is seriously compromised. I also doubt that the Jarrett puppet in the White Hut would ever push the button, unless it was to defend Mecca or Tehran against Joos.