how similar are the languages in south america? (popular ones)
Mostly spanish and portuguese (because of brazil and only brazil speaks portuguese in SA) and they are pretty similar I guess we brazilians can understand they more than they understand us, i dont know why, but thats how a lot of brazilians feel and of course we have some indigenous languages such as guarani. We have french guiana, but its a french territory, so we kind have borders with france.
In terms of vocabulary, it is estimated that Spanish and Portuguese have approximately 89% cognates, which are words that are similar or identical in both languages. However, it is important to note that these words do not always have exactly the same meaning. It's not so difficult to understand the other language even without ever having studied it; nonetheless, it may require some time and concentration.
Yes, obviously the pronunciation is also different, but I believe it's something manageable since there's another way to refer to the same thing. Also, if a Portuguese speaker knows basic Spanish, they won't encounter as many difficulties. What I mean is that with some effort, the languages are mutually understandable to a certain degree, even if they can't speak each other's language.
https://www.youtube.com/watch?v=buqqqVNQHHI and https://www.youtube.com/watch?v=V1B90qhAeMk