Seems to me that if the Soviets in a "limited" scenario bother to bomb something like Broken Arrow, OK, I don't want to know what a total scenario means. The above list adds up to 87,220,305 people with a direct hit.
A lot of those places are suburbs of other cities (like Broken Arrow is of Tulsa), so I'd think they'd count as part of the larger city. (Is Arlington, Va., really a separate target from Washington, for example?). On the other hand, that 87 million figure is city limits only, so it'd fall short. (The effects of a bomb on central Philadelphia wouldn't be limited to the 1.5 million people in Philadelphia...and some people living outside the city limits are actually closer to ground zero than the farthest reaches of the city....) I don't know where the "304 largest cities" bit came from, but I wonder if it doesn't really mean 304 largest urbanized areas - which is what the U.S. census calls a city and the built-up area surrounding it - which presumably covers even more places.
That said, where did you find that list, Atreides? Are those 2010 census figures? I haven't seen a nationwide list and ranking anywhere else yet.