Just like in the comics, Steve and Tony had differing opinions on legislation dictating what enhanced individuals could and could not do, and considering that these two were among the MCU’s anchoring heroes, it felt all the more powerful when they found themselves on opposite sides of both this political debate and later on the battlefield.
It’s fortunate that Kevin Feige and the rest of the Marvel brass were able to sign Robert Downey Jr. onto Captain America: Civil War, as it’s hard to imagine who could have served as Steve Rogers’ heroic opposite in Tony Stark’s place.