Some kind of system that awards individual initiative and self-starting. A market sector would probably be important for a while, and private business would still exist, but I’m guessing they’d be forced to implement worker ownership schemes like ESOPs. There would be government support for cooperatives, and a revived labor movement.
I also don’t think Americans would ever accept a one-party state led by a vanguard party, so a different model of governance would have to be implemented. Cuba has a no-party state, which might be influential.