Brigades?
The columns are rather Regiments, with typical 3 battalions each, with possibility up to 5 battalions. Unless I have missunderstood something.
The game seem to use a mix of brithish and USA terminology. Thus, we get brigades (the equivalent of a regiment in the US and many other armies. Brigade didnt exist as such in the US army, altough they made what they called "Combat Commands") and battallions (which, in the UK were also called regiments).
On the other hand, regiments always had a bit of local flavour. It was more an administrative unit than a combat one. Brigades and battalllions were more combat units than a regiment.
All this is in general terms.