When? Well the next time we are deeply affected by 15,000,000 in armed forces [in today's population, maybe 20,000,000], Rosie the Riveter leaves the office for war production (if she can manage to import the material], rationing, air raid drills, blackouts, and bond drives to raise war funds. In other words when everyone is involved in effort to win.
Would the price of winning be acceptable today? Look at the popularity of a draft and tax cuts.
Winning a war requires more than advocacy from keyboard commandos.
But is the American population sufficiently poplated with enough people to even get us to this point, or are they more likely to surrender and not even fight if such drastic sacrafices as needed during WWI and WWII are needed to win a war today? I have my doubts.