He could meet new professors. These professors would have their own teaching styles and areas of expertise. They might introduce Harry to different aspects of American magic that he has never encountered before.
There would be new students as well. Some of them could be descendants of the original founders of Ilvermorny. They might have stories and knowledge about the school's history that they could share with Harry. Also, he might meet students with unique magical talents, like those who are especially good at transfiguration or potion - making in a different way than at Hogwarts.
In some fanfictions, Harry might find it difficult to adjust to the new magical environment at Ilvermorny. The different houses, like Horned Serpent, Wampus, Thunderbird, and Pukwudgie, would be a new concept for him compared to Hogwarts' houses.
Harry could meet some local magical creatures that are unique to Africa. For example, there could be a magical creature similar to a hippogriff but with different characteristics. And he may also meet African witches who are experts in herbal magic, which they use to heal and protect their communities. They could teach Harry some of their techniques and knowledge.
He could meet Fleur Delacour's family. Since Fleur is from France, her family might be an important part of the French wizarding community that Harry interacts with.
He might meet international aurors. These are highly skilled wizards from different countries who are experts in dark wizard catching. They could teach Harry some new combat spells.
He might meet Canadian witches and wizards. There could be a friendly wizard who shows him around the Canadian wizarding community.
He might meet other Hogwarts students who he doesn't know very well. They could become good friends through their shared love of Quidditch.
He could also meet some sort of dark wizard or villain that is even more powerful than Voldemort in this new world. This would pose a great threat to Harry and force him to use all of his skills and knowledge, both from his own world and what he's learned in the new one, to defeat the enemy.
He could meet Hagrid. Hagrid often goes to Diagon Alley, so it's possible he'll run into Harry while he's shopping and give him some useful advice about what to buy or not to buy.
He could meet an Egyptian wizard who is an expert in ancient magic. This wizard could teach Harry a great deal about the history of magic in Egypt.
He could meet the Dalton students. They might be very different from his Hogwarts friends, maybe more focused on academic magic in a different way.