I immediately thought of the Spanish American War but actually by the 30s we were in a decline militarily. That doesn’t tell the whole story tho.
In the words of Yamamoto, we were a “sleeping giant” which just needed to awaken. The attack on Pearl Harbor was the big one but we had already begun to stir before that.
A good book on that is Freedom's Forge," detailing how we had been marshaling our industrial might in the late '30s up until late '41, so that when TSHTF, all we had to do is ramp up what was already in place. IMO, William Knudsen and Henry Kaiser are unsung heroes.