These 3 are very famous outside the US.
The Kumbh Mela, the world's largest festival attracts 100 million but you'd need to put 4 cities down as it rotates between therm each year. Likewise the largest music festival Donauinsfest in Vienna attracts 3.2 million each year but it's unknown outside the Alps due to it's Austrian band-heavy line-up.
I have heard the name sundance, but that is about it.
because if its by turists, we can use the Carnaval in Rio de Janeiro as an example, it would be in Rio for sure the most famous, yet if you go by the locals/brazilians, most of them prefer the one in Salvador