People who think Bruce would be team cap are so incredibly ridiculous. Like yes he hates Ross and doesn’t trust him at all so i think he would spend the entire time begging tony to remove him from the equation (which, like, literally might have stopped civil war from starting) but he NEVER would have joined team cap. If not for his giant guilt complex that would relish in accountability then because of Wanda. One of the prime motivators for team cap was that Wanda was on house arrest. People rallied behind Wanda in her defense of what happened in Lagos because a mistake was made. Do you think for a second that Bruce would believe that? Or even care? Bruce hates Wanda. Bruce said that he could kill her with his bare hands “wouldn’t change a shade.” Wanda forced him to Hulk out and attack a city in AoU which is realistically the only case where he would feel anger mostly towards someone else, not himself. Dear sweet Bruce is a scientist, and when he can swing it, a pacifist. But he straight up wanted to kill Wanda because of revenge.
In civil war he would try and stop the fighting. He would try and get rid of Ross, which shouldnt be too hard because one of the major concerns for the accords was that the avengers were too American. But if teams were separated and team cap held the treatment of WANDA up as the rallying cry you can be damn sure Bruce is staying with his science bro. Or he’ll just leave again because like I said- pacifist.