Let's face it, Captain America: Civil War would have been a very different film if Thor hadn't headed off to Asgard at the end of Avengers: Age of Ultron. Whichever side had Thor on their side in the airport battle would undoubtedly have been victorious; I rather suspect he'd have enjoyed going at it with Giant-Man, for example! But the question has to be, how will Thor and Loki react to the changes when they get back to Earth?
Well, at Wizard World the actors have been asked just that! Check it out...
Hemsworth clearly pictures Thor as above all this petty squabbling, dismissing the entire Civil War as nothing more than a "tiff". He also rightly points out that Thor's reaction may well depend on just what the context is - Avengers: Infinity War Part I promises to reunite the team around a cosmic threat of the first order, as Thanos comes to Earth.
That said, I can't help wondering if Thor really would be so neutral in all this. I can't imagine the son of Odin being comfortable with the Sokovia Accords, for example; either his actions would be deemed illegal, or he'd be forced to register and report to the United Nations. Remember, in Captain America: Civil War, Thunderbolt Ross viewed both Thor and the Hulk as nuclear weapons the Avengers had misplaced, and there's no doubt that the amount of political pressure brought to bear on the Odinson would be significant.
Over in the comics, Thor was actually dead at the time of the superhero "Civil War" arc. But the events there were far more personal - Tony Stark and Reed Richards actually dared to create a Thor clone (it became the villain known as Ragnarok). So when Thor came back from the dead, he took that personally, and showed Iron Man just how powerful he really was - before refusing to register, and warning the American government to butt out of Asgardian business.
I love Tom Hiddleston's answer.
"Loki's like, 'When I came down to Earth, I brought you guys together. And now I've left, and you're fighting each other. Sorry. So sorry.'"
Let's face it, the comment has just the right tinge of arrogance and mischievousness, and I for one wouldn't be surprised if the line gets dropped in! Then Hemsworth jokes that Loki will be joining the Avengers - and will "lead them all"!
Interestingly enough, in the comics Loki is a fascinatingly complex character. There have been a number of times when he's fought on the side of the angels, and even starred in his own book (I cannot possibly recommend Al Ewing's Loki: Agent of Asgard highly enough). Given the popularity of Tom Hiddleston's Loki, it may well be that he becomes a 'shade of grey' character - sometimes fighting against the Avengers, sometimes alongside them.
Of course, this is only guesswork. As Chris Hemsworth points out, the two actors have no idea where the Marvel Cinematic Universe is going post-Thor: Ragnarok, and right now are looking no further ahead than next year's Marvel blockbuster. It's fun to guess, but only Kevin Feige and the Russo Brothers will have any real idea...