I'm not sure of a specific one off the top of my head, but you can try searching on fanfiction.net. There are likely many great stories there with that premise.
A fanfiction could explore the emotional turmoil the Avengers go through while watching the Civil War trailer. For example, Wanda Maximoff might see the trailer and be afraid of the power she wields and how it's being portrayed as a threat. Vision, on the other hand, tries to analyze the trailer from a logical perspective, but also feels a sense of unease. The team realizes that the trailer is not just a promotional piece but a warning of what could come if they don't sort out their issues soon.
In a Civil War vampire story, vampires could have also affected the war by changing the morale of the troops. If rumors spread about vampires in the area, soldiers would be constantly on edge. This fear could make them less effective in combat. And if some soldiers believed that vampires were on their side, it might give them a false sense of invincibility, which could lead to overconfidence and mistakes on the battlefield.
The trailer story of Shadow of War could be about the power struggle in the game's universe. It may feature the different factions vying for control. For example, we might see the hero trying to unite various groups against a common enemy, which could be a powerful and evil warlord. There could also be elements of betrayal and redemption as the story unfolds within the trailer.
It depends on your preferences. Some people love it for its complex characters and intense plotlines, while others might not be as impressed. But overall, it has its merits.
The Civil War's story was one of conflict and upheaval. Slavery was a major cause, but there were also disputes over trade, taxation, and representation. The war was fought on many battlefields and had a profound effect on American society and the way the country developed.