Something I (an american) noticed about kenyan girls

In america even girls age 18 and well below seem way older than girls in kenya who are in their late 20s. I'm not sure exactly why, maybe it's the culture and lifestyle in America which ages you faster but it's mostly mentally and emotionally they're younger. The girls I met in kenya (there are many) had astonishingly younger presences in every way. They literally didn't seem to be adults to me, and most times their relationship with their parents and homelife reflected this too. I feel like only Americans or people who have lived in america can understand this 🤣 perhaps america is far different than any place in ways we don't realize until we leave. Does anyone have their own explanation or related experience