Before the integration, in early battlefields like Moscow and Stalingrad,
Germany used the 50mm Pak 38 anti-tank gun
while the Soviet Union used the 37mm 53-K anti-tank gun.
In later battlefields like Berlin, both sides used the 75mm Pak 40 anti-tank gun.
However, currently, engineers from both Germany and the Soviet Union install the 75mm Pak 40 anti-tank gun regardless of rank.
While this may not pose a significant issue in high-rank battles, in low-rank battles, the anti-tank gun becomes more powerful than tanks, rendering tank armor meaningless.
Therefore, in low ranks (Rank 1-2 or 1-3), the 37mm Pak 38 and 37mm 53-K should be used as before, while in high ranks, the 75mm Pak 40 should continue to be used as it is now.
addition The United States has the 57mm M1 anti-tank gun,
Japan has the 47mm Type 1 anti-tank gun.
Both of these anti-tank guns are convenient to use in low ranks, but they lack penetration power in high-rank battles. Therefore, the United States and Japan should be provided with anti-tank guns that can be used effectively in high ranks.
Personally, for the United States,
3-inch M5 anti-tank gun
OQF 17-pounder anti-tank gun.
Adding such anti-tank guns seems like a good idea.
Japan has some weapons
According to the document (九二式十糎加農砲 - Wikipedia), the Type 92 10cm cannon is one of Japan’s artillery cannon. Its AP shells could penetrate up to 175mm.
According to this article(https://topwar.ru/159485-japonskaja-protivotankovaja-artillerija-vo-vtoroj-mirovoj-vojne.html) The Type 3 105mm Recoilless Gun had a penetration capability of 150mm
