[AI not following commands]

That shouldn't happen so its not the ai's fault, sounds like human error. Assaulting means the squad splits into two pieces, one stays back and covers while the other maneuvers. Once one fireteam reaches a certain spot they will begin covering and the fireteam behind will maneuver to there position. Unless they were being fired upon or you misjudged placing the assault/movement point there is no reason for the units to "assault a random building".

If a squad sustains enough fire or casualties if they don't get pinned they will attempt to find cover, so if that building you "assaulted" into killed some of them or they took a lot of fire, they will displace and attempt to take cover.

As for vehicles colliding with each other, give them pause commands so they aren't trying to move at the same time in the same spot, this is especially essential when moving in convoy formation. For example, Vehicle 1 (An abrams lets say for the hell of it) is leading the column, you give him a quick command up the road, behind him is a Bradley about 10 or 15 meters, give him a 5 or 10 second pause so he doesn't run straight into the Abrams, repeat as necessary only increasing pause commands on subsequent vehicles.

Their are no mods to fix these "problems" it sounds like you are new so you haven't learned the finer points of it, but I hope what I explained helps you out a bit.

The building I assaulted did not have enemies inside of it. Regardless, you're most likely correct in that it was Human error. I usually don't play strategy games, so I got frustrated when I told each unit a specific order, and did not understand why the units did not follow the orders. I'll probably watch a few youtube videos before I try the game again.

[AI not following commands]

I bought the Combat Mission: Shock Force Marine Bundle, and I am getting extremely frustrated at the AI's inability to follow simple orders. I told one squad to assault a building, but the second they finish clearing the building, they exit and charge right into 2 MGs to assault a random building across the street. I can't even order two vehicles to move without one of them finding a way to collide with the next. Is there a mod or a setting to fix either of these issues?

I want to give this game a try, but I just can't play a strategy game where the path-finding is absolute ****, and the units blatantly disobey half of my orders.