It no longer makes sense to attack the US mainland w/nukes.
It's much cheaper and easier to attack a major US corporation w/a cyber attack, which effectively gives the attacker conquest over the segment of the US law code controlled by that corporation.
For example, a single cyber attack on Exxon, w/sufficient compromising information recovered on corporate board members, would give the hacker complete control over US energy laws and policy.
An equivalent attack on Exxon, Microsoft, Intel, Goldman Sachs, and Time Warner would mean control of 70-80% of the US govt., including total control of US energy policy, copyright laws, banking legislation, security policies, . . .