Steve Rogers and Tony Stark could never be accused of being best buds. There's always been a resentment there from Tony, especially when his father admired Steve Rogers so much, and it's always been simmering in the background. They've worked together as colleagues, to fight the Chitauri invasion of New York and came together again, with the Avengers, to fight Tony's creation Ultron.
But Ultron really was the breaking point for a lot of things in Tony's life. Suffering from PTSD after the events of the Avengers, he truly believed creating Ultron would benefit the world. Now racked with guilt and remorse, and alone after Pepper ends their relationship, Tony Stark sees the Sokovia Accords as a way to make things right.
Steve Rogers, however, disagrees. He's seen what happens when men are given power over others, that freedom isn't supposed to involve fear and that bureaucracy and red tape will only resolve a situation the people in charge want to see resolved. Saving innocent lives shouldn't need to be agreed beforehand by a committee. The Avengers may not be perfect, but they're all the world has.
And so, the Avengers split. It's friends vs friends as tensions reach boiling point after Bucky Barnes is accused of bombing innocent people at the Accords signing, including King T'Chaka of Wakanda. Steve, being Steve, sees a situation pointing south, and he can't ignore it....
I would love to hear your thoughts on Captain America: Civil War, or the entire Captain America trilogy!