You've experienced at least a
double Mandela effect ... Maybe even a Mandela trifecta ...
Cape Horn is at the southern tip of South America (Tierra del Fuego). It's that continent's southernmost headland.
The cape in southern Africa - south of Cape Town, and mistakenly cited as the place where the Atlantic and Indian Oceans meet - is the Cape of Good Hope. The Cape of Good Hope isn't the southernmost tip of Africa. That's Cape Agulhas, circa 150 km farther southeast.
https://en.wikipedia.org/wiki/Cape_of_Good_Hope
https://en.wikipedia.org/wiki/Cape_Horn