Should have said this before, but while I think attacking another country makes more sense I actually suspect that the war with China angle will be over the raid of the consulate, the set up of the nuke didn't look like something capable of a long range strike.
I agree with Welverin. To hit China frow Iowa with a nuke would require a ICBM with a range of over 4,000 miles. The ICBM would have to have valid codes and a silo and equipment specificaly for a missile of that type. The only U.S. ICBM in service that could do that is a LGM-30G Minuteman III. But, there aren't any missile bases in Iowa. And even if there was, the terrorists would have fight though it and make sure the missiles weren't deactivated.
Note: I checked on the FAS website . I don't know this stuff of hand.