Why U.S. destroyers did not immediately adopt twin five-inch mounts

Why did the U.S. Navy adopt twin five-inch destroyer mounts later than other navies?

Because it was balancing gun power against torpedoes, ammunition capacity, and sustained rate of fire, not choosing mounts in isolation.

The U.S. Navy's choice balanced guns, torpedoes, and ammunition. A twin five-inch mount changes the balance with torpedo armament and demands more ammunition than a single mount. Its theoretical rate of fire must also be tested against the sustained rate that the crew and supply system can maintain. Copying a foreign mounting arrangement was therefore no simple one-for-one improvement in destroyer design.