However, the comparison is not so straightforward. World War II managed to eat up a whopping 36% of the United States GDP, while the war on terrorism has just taken around 1% of the US GDP. There are many other factors that differ with time, that make the comparison extremely difficult.
Even the CRS report suggests the same. The reports says, "One problem is how to separate costs of military operations from costs of forces in peacetime. In recent years, the DOD (Department of Defense) has tried to identify the additional 'incremental' expenses of engaging in military operations, over and above the costs of maintaining standing military forces. Figures are problematic, as well, because of difficulties in comparing prices from one vastly different era to another. Perhaps a more significant problem is that wars appear more expensive over time as the sophistication and cost of technology advances, both for military and for civilian activities."
Nevertheless, whether the conflicts are achieving their objective is another matter, but the Global War on Terror cost will go much higher in the near future. According to an estimate in the year 2007 made by the Congressional Budget Office, by 2017, the engagements in Iraq and Afghanistan could cost the United States up to $2.4 trillion.