Complex sentence: There are differing explanations as to why this act was instituted, one of which is that the average Independent Americans regarded Indians control of land and other natural resources in parts around the country as a serious potential threat towards their expansionary and economic goals.
Split into simpler sentences: There are differing explanations as to why this act was instituted. One of which is that the average Independent Americans regarded Indians control of land and other natural resources in parts around the country as a serious potential threat towards their expansionary and economic goals.