[DTogo]

"...rapidly developing a method of blowing up a major U.S. city..."

Is there some other way to do this besides thermo nuclear device, which is not a "method" you develop, but rather an item you procure?

[Pearls Before Swine]

Is there some other way to do this besides thermo nuclear device?

Sure, natural gas storage tanks come to mind. Or railway targeting if you know the schedule for particularly hazardous freight. Nothing new there.