Could they though? You think China would just sit around and let the U.S fire nuclear missiles at them without intercepting them and firing their own? Why are you so sure that wouldn't just end up with a U.S sized crater north of Mexico?

Also, dismissing any predictive situation as some crazy out there "what if" is hilarious.

War games are an extremely important part of any strategy so that you don't just walk right into an easily predictable slaughter because you "don't care about what ifs".