which american tank was considered the heavist duty tank during wwii and what is the modern US heavist duty tank
I need a list of the tanks that saw action during the second world war only

I am building a diorama of the vehicles used in the war but I am a dumb old man 66
grandad43

I think the heaviest American tank was the M-26 Pershing.
modern would be the M1 Abrams at 70 tons

seeing action in WWII for USA
Shermans,Lee's,Grant's,Stuarts probably more but cant think right now,these models also had many variants.

hope this helps some.

In terms of quantity, the most important US tank was the M4 Sherman series. About 48,000 gun tanks were built, plus special purpose vehicles on the same chassis. It weighed around 34 tons (varying according to the particular gun and engine combination). Early models carried a 75 mm gun. Later models featured a long barreled 76 mm gun or a 105 mm howitzer.
The M26 Pershing (originally designated the T26E3), appeared in combat in March, 1945. It weighed in at 46 tons, and carried a 90 mm gun. About 300 reached Europe before the end of hostilities, of which about 250 had been issued to the troops.
Since 1982, the heaviest US tank has been the M1 Abrams. Current model is the M1A2 with a 120 mm gun. Weighs close to 70 tons.

thanks tony,gerald
now me gotta find a pershin tank

Tamiya has a Pershing in 1/48 and 1/35 for sure.