Although I can successfully adjust the game speed in singleplayer mode, the options seem to have no almost effect when playing a multiplayer game in LAN. The game is just unbearably fast.
The successor, American Conquest, has the same problem.

Has anyone a solution to this?

I am having the same issue, would love to play a LAN with a few buddies but the game speed is just crazy, I have heard it is something to do with processors being too fast, will look into this further and report back my findings.

I, too, have this problem. It makes the game unplayable against any AI opponents.