jewishfeminist02: A potato does not resemble a grain, whereas raw quinoa does. Also the way in which quinoa is eaten is similar to that of the traditional grains, unlike a potato. Indeed, quinoa is in most ways more “grain like” in appearance and use than Maize (American corn). So once you hold the quinoa is non-kitniyos, you are left asking whether Maize (American corn) should also be considered kitniyos. This means the real question is really whether we should even hold by a prohibtion of kitniyos since if you start making quinoa bread on Pesach, where do you stop.
But again, this is a question to be decided over time by the gedolim. It took a while for them to settle on what to do with potatos and maize (American corn) when they were introduced to frum Jews in the 16th century.