The Yamoto class had big guns, but they were vastly inferior in fire control to American systems.
The Iowa class used the Mark 13 Fire Control suite. The system was insanely ahead of it’s time. It had a 3cm wavelength to Yamatos 10cm, and almost 25 times the power output.
Iowa had better speed(27 vs 33+ knots), adequate armor, highly-effective guns, and excellent fire control.
Yamoto had unreliable shells and brittle steel armor.