Big task ahead of ya. It's hard to distill an entire continent of diverse countries, landscapes, and cultures into one scent.
For North America, while there are great mountains and forests and tropical islands, what is jumping out at me as something that is unique to North America would be a cactus fragrance. Cactus blossom, agave, aloe, etc. Cacti are in South America, too, but when you think of a cactus you tend to have a very specific concept in mind of SW US/Mexico
Aloe juice as a water replacement?
For South America, one thing that always reminds me of my time there is the smell of passionfruit. Ah, just thinking of the smell brings me warm flashbacks of sitting with a cool glass of fresh juice in my hand. Guava is a good one as well. A completely off the beaten track idea would be chocolate. Ecuadorian chocolate is divine.
Or dulce de leche... ooh. Additives could be Brazilian clays, cocoa butter.
For Asia, a tall order. I think Coconut Lemongrass is okay as it invokes some SEAsian dishes. My experience is with living in an EAsian country, so I'll still give my thoughts. Green Tea is always a classic. Sakura FOs tend to behave badly, sadly. Yuzu, ginger, nashi pear, plum blossom, goji berry, chrysanthemum, jasmine. Additives can be rice water or if you're feeling fancy, fermented rice water (super easy to make~)
For Europe, hnnn. Honestly, I just think of bread. I'm so sorry Europe. Every time I visit you, I just eat too much bread, meat, and cheese.
Lavender, rose? Lemon? Olive? Additives... beer? French green clay?
No Africa journeys from me (yet!), but Moroccan Mint is a solid choice. Spearmint and black tea is a divine scent combination, too. Orange/clementine? Myrrh, sandalwood, amber? This is where you definitely should lean into the shea butter usage. Baobab powder? African Black Soap crumbles?
Haven't been to Oceania, either, so I'll let KiwiMoose keep the podium on this matter. But you could throw our dear Kiwi a bone and add a little honey for New Zealand
Wow, while I was searching out of pure yearning curiosity to see if someone out there made a milk tea fragrance, I found this website that has FO categories for different regions/cultures
. Might be a good place to snag some ideas or even a FO. omg I have FO envy right now just looking at their inventory. I hope these are actually good quality for soap