Just like humans have eradicated species all over the world throughout history, there must have been some extinction going on when they came to America. I'm asking if there are any known cases of his happening when Native Americans were the cause.
We can't say for certain but it appears that there were numerous species of megafauna that were killed off by native americans. Picture giant horses, massive beavers, rhino cousins, etc. In case you're interested, here is an article from a Brown U anthropology professor geared toward students about this subject: http://nationalhumanitiescenter.org/tserve/nattrans/ntecoindian/essays/pleistocene.htm