What was the most influential aircraft in WWII Why?

The Supermarine Spitfire that was the champion British warplane and undoubtedly the most famous WWII aircraft originating from that country. Developed prior to the war, Spitfires in general are regarded as one of the best fighter aircraft ever.

What aircraft was the first designed specifically for close air support of ground forces?

British F.E 2b fighter
Appropriately modified, the British F.E 2b fighter became the first ground-attack aircraft, while Germany produced the first purpose built ground attack aircraft in the form of the Junkers J.I; the Sopwith Camel was another successful early platform.

What was the best ground attack fighter-bomber of WW2?

No question about it: the F4U Corsair was the best ground attack fighter-bomber of WW2 . The F4U dropped 70\% of all bombs dropped by all US fighter aircraft during WW2. It could carry a bombload of 4,000 pounds.

What was the best aircraft in WW2?

Serving in both WW2 and the Korean War, the Vought F4u Corsair is a three bladed, inverted gullwing machine of war. Having numerous encounters with the Japanese in the Pacific, this fighter was hailed as the first plane able to match the feared Zero and was considered as the best fighter in the Pacific theater. 12 Beastly Bomber

What is the best ground attack aircraft in the game?

Possibly the best sum-up of its ground attack performance is found in Republic P-47 Thunderbolt. (Please pardon the single source reference. This one just happened to be very comprehensive and succinct compared with other sources.) Thank you for the A2A!

How difficult was tactical air-ground support in WW2?

It should be emphasized that during WWII, tactical air-ground support was still in its infancy. Hitting small, well armored or shifting targets tended to be a difficult task, especially if the attacking plane had only a brink amount of time to aim at the target.