Another theme could be heroism. Harry is already seen as a hero in the wizarding world, and as an Army Ranger, he continues to show heroic qualities in different situations like in combat or helping his comrades.
Friendship is also a big theme. Harry makes new friends among the Army Rangers. They might not understand his magical side at first, but over time, they learn to accept and rely on him, and he on them. And there could be themes of loyalty too, both to his new Ranger unit and to his old friends from the wizarding world.
A common theme could also be patriotism. As a US Army Ranger, he might be shown to have a strong sense of duty towards his country. Additionally, the stories might explore how Harry's past experiences, perhaps from his original story context, interact with his new role as an Army Ranger.
One of the main themes is the use of military - style strategies in a magical context. For example, how to plan an ambush against dark wizards like you would in a military operation. Also, the idea of loyalty and camaraderie is often emphasized, both within the wizarding group and among the Ranger trainees. It shows how characters from different backgrounds come together to fight a common enemy. This can create some really interesting and complex relationships in the fanfiction.
One common theme is the clash of cultures. The magical world of Harry Potter and the cowboy - like, law - abiding world of Texas Rangers are very different. Fanfics often explore how these two cultures interact and adapt to each other.
One common theme is identity. Fem Harry has to figure out how her identity as a fan of Power Rangers fits in with her existing self. Another is friendship. Often, she forms new friendships with the Power Rangers or other characters in that universe. For example, she might bond with a particular Ranger over a shared interest or a mission they go on together.
One popular 'Harry is an Army Ranger' fanfic is 'Harry's Ranger Adventure'. It has an interesting plot where Harry uses his unique skills from his wizarding world and combines them with Army Ranger training in a really creative way.
A frequent theme is the exploration of the wizarding world's social hierarchy. As a lord, Harry is thrust into a different social stratum. He has to navigate the politics, alliances, and rivalries among the noble families. This often involves dealing with ancient family feuds and forging new relationships. It also includes themes of legacy, as Harry discovers what it means to carry on a family name in a more formal, lordly way.
One common theme is power and privilege. When Harry is nobility, he often has to navigate the power dynamics within the wizarding world's noble families. Another theme is identity. Harry has to figure out how his new noble identity fits in with his existing self - the boy who grew up with the Dursleys.
One common theme is acceptance. In many of these fanfics, Harry's friends learn to accept his autistic traits. Another theme is struggle, as Harry has to deal with the wizarding world which may not always be accommodating to his needs.
One common theme could be how Harry's German heritage affects his relationship with other characters. For instance, it might change the dynamic with Hermione and Ron as they come from different cultural backgrounds.
Common themes often include power dynamics. Since Harry is a demon, he may have new and different powers. Fanfics might explore how he uses or controls these powers, and how they affect his relationships with others like Hermione and Ron. Also, the theme of redemption can be present. Even as a demon, Harry may strive to do good, and the story could be about his journey towards redemption.