The Russians had their A32 tank produced in prototype form by late 1938, with field trials started in 1939.
The British had the importance of low height understood, with their 20 ton cruiser tanks, but no one but the Russians had sloped armour on all sides like the A32 above. The USA, relying on radial engines, fielded the taller M3 Lee and M4 Sherman as their medium tank for the entirety of the war.
I would think sloped armour like this would make the tank easier to manufacture, as it appears to have only five main hull panels (front, sides, rear, bottom), with the sixth top panel being mostly pierced for radiators, an engine access doors, etc.
In OTL it wasn't until the mid-1942 that the US had started designing a low and slopped tank concept in the T-20 series. And the T-20 was only sloped on the front panel, without the A32's side sloped armour.
So, without ASB, how do we get a mass produced, sloped armour, low height medium tank into the Western Allies hands by early 1941 instead of the M3/M4 and UK cruisers?