Yamato intelligence and the Montana-versus-Iowa choice

Would discovering Yamato's 18-inch guns have caused the Iowa class to receive 18-inch weapons?

Probably not; it more likely would have increased priority for the twelve-16-inch-gun Montana class.

Discovering Yamato's 18-inch guns is expected to strengthen the case for the twelve-16-inch-gun Montana class. The United States is considered unlikely to adopt its own 18-inch gun because it disliked the rate of fire and handling difficulties. Montana would provide the more heavily armed battle-line response, while Iowa emphasized speed. This is a proposed shift in construction priorities, with continued use of the 16-inch gun.