“ In a future peer conflict, the US Army will not be granted a six-month, uncontested build-up phase, nor will it operate under friendly skies.”

Depends how the war starts. Russia? USA somehow attacks? Easily 6 months of buildup in Europe.

China? Again USA somehow attacks? Again buildup in Australia, Japan, Korea.

Also US air power is absolutely supreme. I don’t see how they will be fighting in actually contested skies even only 2 months in.