That ain't going to happen.
Nuke goes off in NY, or Dallas or New Orleans, etc., and I guarantee you that there will be nuclear retaliation against any identified source within 90 minutes, max.
Nuke goes off in such a way as to take out the President or any significant portion of our government and there will be a general bombardment of that entire region.
Nuke goes off anywhere on the planet and marshal law will be declared, all potential enemies will be warned to not approach our assets anywhere in any way, shape or form, and no ship, plane or any other form of transportation will be allowed within 50 miles of our borders.
Oh, and troops will be deployed with shoot to kill orders at all borders and ports.