Another plot could be that Lelouch's Geass power is discovered by the British in America (assuming they still have some influence). They try to capture him and use his power for their own imperialistic goals. Lelouch then has to team up with the local resistance in America, using his Geass sparingly and cleverly to outwit the British and help the Americans gain their freedom in a more unique and exciting way compared to the actual historical events.
One possible plot could be Lelouch finding himself in Washington's America and using his Geass to influence the political situation. He might encounter key historical figures and use his wits and power to change the course of events in a way that reflects the complex themes of the original 'Code Geass' series.
Suzaku could be another main character. His conflicted loyalties in the original series could be translated into this new setting. He might be on the side of the British at first, but then have a change of heart after seeing the injustices they are committing in America. His piloting skills could also come in handy, perhaps in battles against the British forces that have advanced mecha technology, similar to the Knightmare Frames in the original 'Code Geass'.
Perhaps in the fanfic, Code Geass technology somehow finds its way into George Washington's time. He could use it to outwit the British forces. For example, he might use a Lancelot - like mech to turn the tide of a battle. The story could also explore how his values would interact with the often morally gray world of Code Geass.
One possible interesting plot could be a crossover where Mario, from the Mario universe, somehow gets transported to the Code Geass world. He might use his unique abilities like jumping and power - ups to help the resistance in Code Geass against the Britannian rule. Diesel could be some new type of mecha or vehicle in this fanfic that is created by combining the technology of both worlds. For example, Mario could use his plumber skills to fix the Diesel mecha when it breaks down during a battle, adding an unexpected yet fun element to the story.
Well, a significant theme is the clash of cultures. The unique culture of Code Geass meets the American culture. This can result in interesting scenarios where the values of loyalty and honor from Code Geass mix with the American values of freedom and opportunity. Also, the theme of justice is common. With Geass being a powerful tool, questions about who has the right to dispense justice and how it should be done in an American - style society are often explored.
A fanfic could center around Cornelia's relationship with her sister, Euphemia. It could show their sisterly bond, their differences, and how they support or oppose each other in the complex world of Code Geass.
He could be a rebel leader like Lelouch. Just as Lelouch fought against the Britannian Empire, Washington could fight against an oppressive regime in the Code Geass world. His leadership skills and strategic mind would be valuable assets.
One interesting Code Geass USA fanfiction could be one that explores what would happen if Lelouch had to operate within the complex political landscape of the United States. Maybe he would use his Geass to influence politicians and manipulate the power structures in a different way compared to the original setting. Another could be a story where the American resistance against Britannian rule is led by an original character inspired by the Code Geass universe, with unique mecha designs and battle strategies.
A character could be a young American soldier who discovers he has the Geass power during a war. He then has to decide how to use it. Will he use it to end the war quickly at any cost? Or will he try to find a more ethical way to use it to protect his comrades and his country?
Perhaps in this fanfic, there could be a group of American rebels who use Geass to fight against an oppressive regime. They could form an underground movement, using their Geass powers to gather information, carry out covert operations, and ultimately strive for freedom and justice in a world that has been turned upside down by the power of Geass.
One plot idea could be exploring Cornelia's relationship with her subordinates in a more in - depth way. Maybe she has to lead a risky mission and how she overcomes the challenges within the team. Another could be a story set in an alternate universe where Cornelia has to make different choices that change the fate of the Britannian Empire.