Trump insists it's very normal for the winners of wars to pay billions to the losers
(www.thebeaverton.com)
I don't think the USA just forgot about it, ISIS was never a real issue, just a anther cause for endless proxy wars, it's a machine that works as intended.
"Nation building" after WWII wasn't free or benevolent at all (USA or USSR), the tactic was to control the nations instead of letting them regain full independence - as much as/in a form a post-British-empire world can allow imperialism.
(Israel was a form/consequence of this 'nation building' as well.)