I think US hiked tax rates to finance the war because of the gold standard. Once it was cancelled the government was able to finance military operations simply by printing more dollars, coupled with other crypto-like tricks for artificially driving demand for USD:

- economic/millitary aid to various countries around the world ("airdrops" in crypto-speak)

- petrodollars: denominating oil prices in USD (similarly how Ethereum prices its gas in ETH, and makes ETH the only allowed medium-of-exchange to purchase ETH)