Why couldn't the US make a battleship better than the Yatamoto?

The US didn't know about the Yamato, she was built in secret. The US did make battleships better than the Yamato; the Iowa class and the Washington class. The Yamato class was bigger, but not better. The Montana class battleships were planned to be comparable in size to the Yamato, but it was decided to build more aircraft carriers instead. The Yamato and Musashi were sunk by US aircraft carriers.