CoOp with computer skirmish mode
 

How to play skimish mode in one side with cpu ? Like in first american mission. There is some mod or someting?

you mean with allies?
cause that is easy to make with the gem editor
just open the mission you want and put all the soldiers you want, owned by other player, of course and after that go to mission edit mode (press F3) and press F9 to mission properties; click on diplomacy and check the player that owns the "allied units" and your own and set the block color to green, then you got your allies.

obviously you will have allied soldiers without scripting, meaning: they get alerted by an enemy, they will get crazy and chase it to the end of the map, haha BUT READ THIS CAREFULLY: MAKE SURE THAT ALL THE ALLIED SOLDIERS AND VEHICLES HAVE THE MOVEMENT MODE SET TO MOVE AT WILL.