A dinosaur-killing asteroid hitting China isn't going to do much good for the US. Kill off your largest competitor (and supplier) along with the rest of Asia, a

A dinosaur-killing asteroid hitting China isn't going to do much good for the US. Kill off your largest competitor (and supplier) along with the rest of Asia, and then watch the ejecta fall back down around the world as they superheat the atmosphere and burn forests. Then look forward to dealing with a starving and freezing population as thick clouds envelop the planet for several years.