The military could be quickly expanded like 1942, although the population is decided less capable than then.
The real issue is the disappeared industrial base, which would take decades to restore.
“The real issue is the disappeared industrial base, which would take decades to restore.”
Yep, plenty of people we can draw in for human waves. But the industrial base is spread all around the world, with much of it in neutral countries (or worse). Good luck with that!