system
Given the following post, respond as if you're commenting on Reddit:
human
[Civil War] How might things have turned out differently if Thor had been present during the "Civil War" events?
gpt
Probably relatively similar to how things worked out with Black Panther.

As an alien sovereign, they have no explicit authority over Thor, but they can maneuver things around him to their interests and his.

Thor is short tempered, but he's not about to go to war with most of Earth's governments.  He's also not going to be at their beck and call.  So he can't overtly help Steve's side, but he also isn't going to be a thrall on Tony's side either.  At best, he can cooperate with Tony like T'Challa, which he might do in the interest of keeping the Avengers together for the greater threat he can see forthcoming.

**Ultimately, he doesn't really end up participating.**  Even if he feels the Avengers need to stay together for the greater cosmic threat, you can't beat Steve into submission and arrest him *into* teamwork.  He's not going to upend Earth's own governance and dissolution of the Avengers for the sake of Steve's friend... a warrior's duty is to his people and not just his comrades in the field... but beating Steve up isn't going to do anything either.  He stays out of it and doesn't go to Germany.  He stands as a second voice establishing the unity of the Avengers is more important to the cosmos than petty politics, personal sacrifice, individual loyalty or autonomy or familial division... making Steve even more stubborn and less sympathetic to the audience by putting the fate of one single friend ahead of the safety of the known realms and beyond.

That said, if the matter becomes intractable, he might offer Asgard as a safe haven to preserve what remains of the team until the appointed time... rendering Black Panther somewhat irrelevant.

Basically, the story doesn't work unless Thor is conveniently missing.

If, for some inexplicable reason, Thor participates in Germany, Steve's team is arrested.  End of story.  Too many places where Thor's intervention wrecks Steve.  Giant Man is nothing.  Thor is able to catch the Quinjet in Avengers to get Loki, so Steve's not getting away.  Thor probably can save Rhodey, so Iron Man is still free to catch or stop Steve.  His area-effect attack alone has the potential to stun and drop all of Steve's team.

I don't see Thor motivated to arrest Steve, but if he wanted to, there's little they could do to stop him.