Cuomo is right. U.S. citizens are free to move/travel from state to state. And they are
The only thing to stop that would be imposition of Martial law.
In a place like Communist China, the Chinese Communist Party can shut down an entire city, enforce the shutdown with the military, and create a situation where to attempt to leave a particular city or region will result in one's death.
That is not the type of system we live under in the U.S.
So for me, that means, the cat's outta the bag. There is no stopping the transmission of this virus in the U.S. and the move will likely be toward strengthening the medical community in terms of infrastructure, manpower, and supplies.