Is it so difficult to run a command economy?

Yes, it is very difficult when there is no absolute power, when there are many powerful interest groups with strong support bases, when the rule of law and constitutions are supreme, like the USA.

In the most recent case of the unmasking of a secret agent by a top govt official, only in the USA that the culprit can be brought to task. There is not only a separation of power, but the opposition