...you might want to re-read that article. Several times it mentions the US attacking for the purpose of delaying Iranian nuclear programs, but it never even alludes or hints at America itself using nuclear force.

Yes it does on page three of the article.

"The targeteers honestly keep coming back and saying it will require nuclear penetrator munitions to take out those tunnels," said Kenneth M. Pollack, a former CIA analyst. "Could we do it with conventional munitions? Possibly. But it's going to be very difficult to do."