Stuff being blown up still counts towards production, but it doesn't actually add any value. Changing tanks in storage to tanks blown up on the battle field isn't actually good for the economy, it just looks like it for some metrics.
The US economy (and much of the rest of the world) actually went into recession after ww1. Then after ww2 you have to consider that the US was one of the very few industrialized countries that didn't get its cities blown up. The war was 'good' for the US mostly because it was much worse for everyone else.
Stuff being blown up still counts towards production, but it doesn't actually add any value. Changing tanks in storage to tanks blown up on the battle field isn't actually good for the economy, it just looks like it for some metrics.
You could say about the US during WW1/WW2, but look at their economy leading up to each war and following it.
The US economy (and much of the rest of the world) actually went into recession after ww1. Then after ww2 you have to consider that the US was one of the very few industrialized countries that didn't get its cities blown up. The war was 'good' for the US mostly because it was much worse for everyone else.
But not during the war. The US did well after the war because Europe and Asia were wrecked by war and America wasn't.