Okay, so just in general, this is a bad idea. Trailers are not designed to provide useful information about movies; they are designed to provoke interest in seeing the movie, not remotely the same thing.
That said… okay, let’s talk about Captain America: Civil War based solely on the trailer that just dropped.
First off, it’s kind of neat how the positionalities of Stark and Rogers have swapped over the course of the MCU films. Initially Stark was the rebellious “bad boy” and Rogers the good soldier, but their experiences have changed them. Now, as the moral center of the MCU, Rogers naturally opposes a policy almost certainly rooted in fear of the Other and the desire to control and weaponize the abilities of “the gifted” (to steal a term from Jessica Jones) while Stark has positioned himself as a protector, so of course to him the fear of the Other is only natural.
And therein lies the dilemma with this film, because… look, any genre, by its nature, has assumptions built into it, and those tend to lead towards particular philosophical, political, and aesthetic positions. That isn’t to say that any work in the genre necessarily endorses or expresses those positions, and still less that those are positions held by the writers or even the characters, but rather that the genre has a sort of gravitational pull that must be actively resisted if you want your work not to fall into those positions. So, for example, a story of aliens infiltrating our society with malicious intent is naturally going to pull toward xenophobia and hostility toward immigrants, and requires active effort to construct a story that resists that reading. High fantasy tends toward nostalgia for an idealized pre-modern Europe, which pulls toward very regressive politics. Anything which is about fear of the radically Other is going to pull toward racism.
And superheroes… well, they’re stories about how society is under constant menace from powerful, unsavory individuals and organizations that threaten it, against which we are helpless. All we can do is cower and hope to be rescued by specific individuals endowed with superior moral fiber and physical abilities. That’s some pretty ugly politics, right there.
So it makes sense to have superhero stories that interrogate their behavior as vigilantes. Who can be trusted with this kind of power, and how do we make that decision?
These are good questions… but they run afoul of the serialized nature of superhero narratives, and that includes the MCU (which, so far as I know, has no more plans to ever actually end than Marvel Comics does). Quite simply, the final conclusion must be that having vigilante superheroes is the correct answer, because otherwise we don’t get superhero stories anymore. (Of course some heroes can work for the government, for a time, but their essential nature as vigilantes means that they will inevitably either eventually go rogue, or else be given so much freedom to step outside the normal rule-of-law limitations that (supposedly) restrain government agents that they might as well be vigilantes.)
Which means that of course the MCU’s moral center is on the side of rampant unrestrained vigilanteism, because the MCU necessarily must be on the side of rampant unrestrained vigilanteism, because that’s what we’re all buying movie tickets to see. Which, in turn, makes it that much harder to resist the strongman politics inherent to the genre. Which is a roundabout way of saying that I fully expect Civil War to be at best incoherent, and at worst actively regressive.