The odds of NK SUCCESSFULLY lobbing a nuke at the U.S. are not all that great. About as likely as one of those novelty contests where a guy throws a basketball from one end of the court to the other and if he makes a basket, wins a million dollars.
In NK's case, if they got in a lucky shot, it would be the end of North Korea, and Pyongyang goes down in the history books with Hiroshima and Nagasaki, and rightly so.
No matter what Moscow and Beijing may think (or not think) of us these days, they have no doubt communicated to Kim Jong ILL that they would look most unfavorably upon him doing anything stupid, because they know that any nation stupid enough to fire a nuke at the U.S. will cease to exist, and radioactive fallout does not recognize any national border, i.e., Russia and China have no desire to have fallout raining down on them due to the moronic notions of KJL.
If push comes to shove, and if Beijing and/or Moscow KNEW without doubt that KJL was preparing to launch a nuke at the U.S., they might take him out themselves in order to be on the 'right side'.
"Russia and China have no desire to have fallout raining down on them"
Actually I think the wind would blow to the east & southeast.
Oh yeah! China could afford to lose a couple hundred million subjects. We can't.