Well, perhaps the US soldiers go back in time to the era of the American Revolution. They find themselves in the middle of the colonies' fight for independence. Some might try to blend in and help the revolutionaries in a more covert way, while others may accidentally expose their modern ways, causing both amazement and suspicion among the colonists. And in the process, they learn a great deal about the roots of their own nation.
One possible plot could be that a group of US soldiers are sent back in time during a military experiment gone wrong. They end up in a crucial historical battle, like the Battle of Gettysburg. They use their modern military knowledge and advanced weaponry (to a certain extent if they still have it) to change the outcome of the battle, which then has a ripple effect on the course of history.
In a 'us soldiers back in time fanfiction', they could be sent back to World War II. They might land in the European theater. They could end up working with the Allied forces in unexpected ways. For example, they could use their knowledge of modern tactics to help plan a major offensive. Or they might interact with soldiers from different countries and cultures, learning about the hardships and heroism of that time period while also trying to figure out how to get back to their own time.
A young and inexperienced soldier named Jake could be a main character. He's fresh out of basic training and is suddenly thrown back in time. His naivete in the face of this new and old world at the same time makes for an interesting journey as he has to quickly adapt. Another could be Sergeant Thompson, a tough and battle - hardened veteran who uses his experience to lead the group of soldiers in this strange time - travel situation.
One possible plot idea could be a team - up scenario. The RWBY characters might encounter a group of US soldiers in a strange, otherworldly dimension. They would have to combine their skills, with the RWBY girls using their unique combat abilities like Ruby's scythe - wielding speed and the soldiers' military tactics and weaponry to face a common enemy. For example, they could be fighting against a horde of Grimm that have somehow invaded a world that has elements of both Remnant and a modern - day Earth setting.
Perhaps Sasuke goes back to the very beginning of his ninja training. He decides to learn different jutsu that he didn't focus on before. He could also try to understand the political situation of the village better. Since he has seen the consequences of certain actions in the future, he aims to change things for the better. For example, he might try to improve relations between the Uchiha and the rest of the village much earlier. This would involve interacting with the elders and trying to find a compromise. It could also lead to a different path for Itachi as well.
One possible plot for 'Titanic Back in Time' fanfiction is that a modern - day historian goes back in time to the Titanic. They want to study the ship and its passengers up close. However, they end up getting involved in the events on the ship. They might try to document everything in a different way, perhaps to prove some theories they had in the present. And as they interact with the people on the Titanic, they start to form deep emotional connections and struggle with the knowledge of the impending doom.
One possible plot could be Gohan going back in time to the Saiyan saga. He could use his knowledge of future events to prevent certain tragedies. For example, he might try to save the Saiyans from Frieza's wrath. He could also train with the younger versions of Goku and the other Z - fighters, sharing his advanced techniques and knowledge, which would significantly change the power dynamics in the battles against the Saiyans and later enemies.
Perhaps in this fanfiction, Damon goes back in time to a period in history that has always fascinated him. He could get involved in historical events and even fall in love with someone from that time. His actions in the past would then have unforeseen consequences when he returns to his own time, like new enemies or allies emerging because of what he did in the past.
In the 'kenichi goes back in time fanfiction', it might be that Kenichi goes back to a time when his martial arts dojo was first founded. He could then meet the founders and learn from them in a more direct way, and also influence their development of martial arts with his modern knowledge. This would create a loop of knowledge exchange between different time periods in the world of martial arts related to Kenichi.
One possible plot could be that Kagome goes back in time and tries to change a major event in the past. For example, she might try to prevent a big battle that had a lot of casualties. She could use her modern knowledge and skills to her advantage in the past, like using first - aid knowledge to save lives.
Perhaps Elsa goes back in time to meet her parents again. She could learn more about her powers from them, as they might have known more than she initially thought. This encounter could also give her a chance to say goodbye properly, which she didn't get the first time. And it could lead to her having a better understanding of her place in the kingdom and her family.
In a 'kaneki goes back in time fanfiction', perhaps Kaneki goes back to when he was still a normal college student. He then decides to study more about ghouls secretly. He could use this knowledge to try and find a way to co - exist peacefully between ghouls and humans from the very start. He might start by trying to change the views of some key people in the CCG, using his understanding of their future actions.