I agree that the US did manufacture some fine pieces of kits during the war. By 1945 they had the best air and sea power in the world and the 2nd strongest land forces.
However, the US started behind in many areas at the start of the war.
Rolling into WWII they had the Grant Tank, which was not the best design (originally had a small turret gun 37mm if i recall, but hasetley upgraded to carry a 75mm in a front mount with poor traverse)
The Sherman started off rough, but once they switched to diesal engines it didnt erupt into flames as readily as the first run petrol engine Shermans.
The Sherman was a fine medium tank, and thats probably where people get the misconception that it was a poor tank. It was never intended for the heavy tank role (The Pershing, which arrived too late to make a huge impact was in that role). All the anecdotes and accounts of Tiger tanks slaughtering Shermans is due to a mismatch of Heavy vs Medium tank.
If you put the Sherman against its equivalents on the Russian and German sides (The t-34 and PZIV) its compares favourably. Probably not as good in a stand up fight as either of those two tanks, but quite agile and had good operating range.
Defensive warfare favoured the German Heavy Tanks, they could sit in a covered position and wait for the Shermans to come to them. However, as the Battle of the Bulge showed the German Heavy tanks were limited in offensive operations due to slow land speed and high fuel consumption.
The Sherman was a great infantry support tank and mobile fire unit. They could be rapidly deployed and filled a myriad of operational requirements.
It is that flexibility of operational deployment that makes me think they are a good tank.
PS. The fighter you referred to was the P-51 Mustang, and it was a beast of a fighter, argueably the best propeller fighter in WWII. While very good it was numbers that held the sky over Germany in the later war as the Germans never fell behind in fighter technology, what they lost were skilled pilots and the ability to manufacture enough planes.