Piracy can only be done by privately owned boats not state actors. There is no term for when a state starts stealing privately owned ships. (because its stupid)

What usa is doing is the crime of aggression which is forbidden by the UN charter. They are just saying they plan on committing aggression against privately owned ships of more nations. But since the UN charter is a dead letter there will be no legal repercussions.

I imagine that China and Russia will start escorting convoys. Then some american owned boat is gonna get taken by plausibly deniable pirates and we will likely end up in a world where all shipping will happen under guard.