There is a difference between sea control and sea denial.
Submarines are fine for sea denial.
But if you are talking about breaking a distant blockade, you need forces which have presence to control the seas and allow cargo ships to run. That means surface ships and locally based airpower.
You need to consider the likely scenario, not the worst case scenario, when planning your military budget. Clearly, trade in the Pacific is mainly with U.S., so it will not be blockaded. Trade through the Indian Ocean is with Europe and the Gulf states. The U.S. will not blockade trade with Europe since they are our allies. Blockading the oil trade is also unlikely because, China has land supplies via Russia. China can also quickly create land supplies or a short hop through the sea from Iran to Pakistan. If China provide a missile shield, the blockade will fail. If China has, say, four CSGs, and keep them close by, it will have far more availability when it needs them in a blockade compared to the U.S. fleets because they don't need to go half way around the world in their normal operations. The idea of a blockade is a fanciful idea. If it is advantageous, it would have happened by now. The further into the future, the less likely it becomes because balance between the U.S. and China narrows in all areas.