For example the most successful clubs and most powerful in South American history are Peñarol, Boca Jrs, Nacional, Independiente, River Plate, São Paulo, Gremio, Flamengo, Palmeiras and Santos. What other do you think are great or never heard of this top 10 from the Americans clubs?
Peñarol and Nacional from Uruguay and Boca Juniors from Argentina and Sao Paulo are the only ones from South America who has 3 World Cups of clubs. So to me they are the best ones.
Realistically speaking, none of them. 99% of football viewers watch European leagues and the rest might as well watch the Saudi League which is full of star players, if they want to try something new. Nobody really cares about these clubs outside of South America.