I consider the United States Navy even in its below 300 ship doldrums as the mightiest fleet on earth, bar none! I also believe it was built to fight the wrong war.
Most dominant seapowers desire with each new conflict to refight some glorious past victory over its enemies. The British Royal Navy up until World War 1 most desired to refight the battle of Trafalgar, when in 1805 Admiral Nelson defeated the French Navy and secured its control of the sealanes for over a century.
When its Trafalgar finally came during the 1914-1916 war, instead of the decisive exchange of broadsides the English most desired, they were forced to contend with submarines, mines, torpedoes, and the first primitive aircraft at sea. Needless to say the Royal Navy was quite annoyed when their German antagonists failed to fight in the expected manner.
The problem here is no other power on earth either duplicates our powerful carrier forces in number or quality of training. Potential rivals at sea like China, Russia, and Third World powers have found it far cheaper to circumvent our unstoppable battlefleet with submarines, fast attack craft, and cruise missile armed naval bombers.