When the Americans were battle-tested at the Kasserine Pass in Tunisia in 1943, they failed miserably.
China is facing a similar situation, with a large military slowly advancing in technology but lacking any real combat experience. But where will China face its Kasserine Pass?
Despite superior numbers and newer equipment, the Nazis handed the US their butts, and combat experience made the difference. The Nazis had been fighting in North Africa for almost three years by then and the Americans hadn't seen combat at all. The Americans were rigid and inflexible, while the Nazis already had time to work out all the kinks in their command and control.
At the time, it looked pretty bleak for us... but we all know Tunisia was just a warmup for what would come later.