USA vs any other country = ?

I have heard numerous individuals claim that the USA would not be victorious in a war against China or Russia: a claim that is in my opinion unfathomable and reeks of falsity. If one were to simply look at military might (nuclear weapons excluded), the USA is unparalleled by anyone in the world when accounting for talent, weapon caliber, experience, spy intelligence, and defensive weaponry. Therefore, what country would dare challenge the mere might of the USA not to mention the unrivaled economic power of the USA? However, China’s recent provocative acts in the South Sea are an anomaly and it thus begs the question: Is China merely bluffing or does the lion actually think it can kill the bull elephant?