See this previous thread for some additional discussion.
Basically, you’re right that the Allied tanks weren’t great at fighting other tanks, and could have been improved. But there’s a hidden assumption in your OP and an outright mistake.
The hidden assumption is the idea that the purpose of a tank is to fight another tank. That’s only true if the military in question wants to do it that way. The American concept was to use different weapons for tank killing – notably purpose-built tank destroyers, anti-tank guns, aircraft, and (in a pinch) bazookas for tank-killing.
American medium tanks (primarily the M-4 Sherman and its predecessor, the M-3 Grant/Lee) were general-purpose tanks, designed to fight infantry and obstacles and, above all, to maneuver at speed. As such they were reliable, fast, and had good suspensions for crew endurance during sustained drives. Fighting other tanks – especially heavy special-use units like Tigers – came as an afterthought.
It is certain they could have been made better for that task, but bear in mind that the theory behind their design was that they were not really for fighting other tanks – you’d have to persuade the US military of the need to make them anti-tank specialists before you could set about upgrading them.
The “outright mistake” is to say the T-34 falls down in comparison to German armor. The T-34 has been called the best tank of the war by many authorities – even perhaps a majority – and its only competition for that title is the Mark V Panther, which was designed based on captured T-34s. Furthermore, the T-34 is often considered the best tank of all time when lists are made. The T-34 was superior to anything the Germans had when they first met it, and at war’s end was still the equal of any medium tank in battle. The T-34 was fast and reliable, had fantastic cross-country and bad-weather performance, and used solid armor, well-sloped, combined with a good gun. Basically the main area of the Panther’s superiority was better optics/rangefinding for long-distance engagements. You can mitigate that somewhat by using terrain to close without exposing yourself to long-range fire – and the Panther was notoriously subject to mechanical failures.
Comparing the T-34 or Sherman to the super-heavies like the Tiger is not as meaningful as one might think, when one compares the numbers involved.
German armored vehicle production in WWII
Soviet armored vehicle production in WWII
American M-4 Sherman production figure: 49,234
Scanning those cites, you’ll see that Tiger production for the war was 1,368 – set against 49,234 Shermans and 57,339 T-34s. Add to that the fact that the later Tigers had difficulty even reaching the front, once fuel was scare and railroads and bridges had been largely destroyed, you’re looking at a Tiger encounter being rare and unusual in the first place.
edit: I see I’ve been scooped a few times.