Well there used to be a good deal of missile silos out that way during the Cold War (but more in the Dakotas) still at the time that might have been their max range.
All that being said we have attack plans for nuclear war just like they do so really I do not see the problem.We have equally deadly plans for China and Russia in the event of a nuclear war.
It seems like that is more of a fallout map the area they would mast want to hit especially in a first strike would our silos scattered across the Dakotas and parts of Washington and Oregon.
@Red they can hit every square inch of the US.
Here is a link to a PDF by chapter on a study of a war between the US and China.Interesting but more strategic rather than the saber rattling Chinese news and the saber rattly counters already linked.
http://www.nukestrat.com/china/chinareport.htm
whole book in one PDF
https://www.fas.org/nuke/guide/china/Book2006.pdf
The US knows much about China we just do not brag about it like they do.Spying is only so useful after all it is not the only tool and is only tool that is used to estimate.
With over a billion citizens there are plently that will take coin for spying against their own government or will do it for other reasons.