It is very unlikely for the US to use nuclear bomb against North Korea, even if it was bombed with some nuclear device by the North Korea.
Is it possible for North Koreans use nuclear weapon against the US?
There is always a possibility. To deny it is not wise. If they are not using it today, they will use it tomorrow, or next year. So to snub the cigarette end is priority.
Will the US retaliate with nuclear weapon?
May be not this time. The enemies may throw one or two nuclear weapons, but it will not be like gunfire exchange. The US needs to think of the next step. If they can eliminate the enemy leaders they will do it. If the leaders are not located, then they will use other means to locate him. They will not burn the whole country into radioactive ashes but not finding their leader.
Are ground forces needed?
The best choice is to use the Chinese army as ground force. North Korea is not like Middle East. There is no rebel army. And the South Korean is reluctant to fight, or simply too weak in their will to fight. There will be an endless nightmare if the South Korean were fighting against the North. They will keep losing and retreating, same as the South Vietnam situation.
To bring in the Chinese needed wisdom. The US has had so many talented people in the Government; they knew how to do it.
9087 Will the US use nuclear against North Korea 20170426
(#The author is a question raiser. He has raised more then 9000 questions. The above article is question no.9087 . He is an expert on cultures and he is a qi master as well as a songwriter. )