The U.S. Air Force has been accused by some, including me, of neglecting close air support to ground troops. The outstanding Republic A-10 Warthog of the past several decades fixed this deficiency, though the A-10's days are numbered. It may be that precision weapons, like the small-diameter bomb that's now operational, will allow fast jets like the F-16 or F-35 to fill the A-10's shoes; the jury is still out on that question.
But in the days of the Army Air Corps and Army Air Forces of the 1930s and 1940s, there were a number of attack aircraft that were designed for support of ground troops. These were either single-engine light bomber size or twin-engine medium bomber size.
The first to play a part in World War II was the Douglas A-20 Havoc. The A-20 first flew in 1939 and was in production for most of WWII. About a third of the 7,478 produced went to the USSR, but the USAAF used the A-20 in all theaters. A-20s carried bombs and many were used as strafers.
https://en.wikipedia.org/wiki/Douglas_A-20_Havoc
The USAAF also bought two types of Navy dive bombers: The Douglas A-24 Banshee (Navy SBD) and the Curtiss A-25 (Navy SB2C). The A-24 saw action early in the Pacific war but did not shine in Army service. The A-25 fared worse; the USAAF ordered A-25s and then turned them back to the Marines -- the A-25 never saw action. (No photos of A-24 or A-25).
The definitive attack aircraft of WWII was the A-20's successor, the Douglas A-26 Invader. The A-26 entered combat in 1944 and proved useful, although for a close air support aircraft the visibility was rather poor. It was built both with a clear nose for a bombardier and with a gun nose; Some late strafing versions had up to 14 forward-firing .50 machine guns! 2,503 were built and the A-26 survived into postwar service. Confusingly, it was redesignated B-26 in 1948, by which time the earlier Martin B-26 Marauder was no longer in service.
The B-26 was very active in the Korean War. The attached photos show B-26s in both natural metal finish and black paint for night missions.
The B-26 continued to serve well after the Korean War as well. The CIA used B-26s painted up in Cuban colors to support the Bay of Pigs invasion in 1961 (see photo) and the B-26K, later re-redesignated A-26 (!), served as a counterinsurgency aircraft in Southeast Asia and Vietnam.
Even the Navy got in on the act, obtaining a few surplus A-26s which were used in utility squadrons to tow gunnery targets and to launch target drones for fleet training. These were some of the most colorful aircraft in the Navy, designated JD-1 (new UB-26J).
https://en.wikipedia.org/wiki/Douglas_A-26_Invader