Where do you start? Prior to WW2 the US was a hodgepodge of competing inefficient intelligence networks. The Army Chief of Staff was the coordinator of military intelligence and J. Edgar Hoover spied on everyone else. Together they couldn't find Kate Smith in a phone booth. Along came Wild Bill Donovan's OSS (Office of Strategic Services). Donovan spent more time trying to convince FDR that an espionage agency was viable than he spent in the field. The Military intelligence network stabbed Donovan in the back every chance they had and Hoover had FBI agents spying on OSS agents. FDR didn't trust Donovan who was an old line NY republican and seemed to relish the political intrigue and in-fighting. Meanwhile the efficient British espionage network was reluctant to share any information with the OSS or the FDR administration. A critical moment for Army intelligence came during the lull in fighting when rumors went around about the Troops being home for Christmas in 1944. The Battle of the Bulge was perhaps the greatest failure of Military intelligence in American history.
And the US intelligence communities long history of failures continues even to this day.
Of course the argument can be made that we don't know about their successes, but consider some of the the failures: North Korean invasion of S Korea; Berlin Wall, Missiles in Cuba, Kennedy Assination, KIng Assination, Kennedy assination; Tet offensive; 72 War in Isreal; Fall of Iran; and opf course everything having to do with 9-11.