Final answer:
The effects described relate to the European colonization of the Americas, which led to a sharp decline in native populations due to disease and violence, alongside the disruption of their societies by military, economic, and religious means.
Step-by-step explanation:
The combination of rapid population decline, increased violence toward outsiders, collapse of traditional social structures, and abandonment of traditional belief systems primarily describes the effects of European colonization and the introduction of diseases on the Native American populations. The European colonization led to a drastic decrease in indigenous numbers due to violence and diseases like smallpox to which natives had no immunity.
Colonizers imposed new economic systems, such as the Encomienda System, depriving indigenous people of resources and forcing many into servitude. This process was exacerbated by the establishment of Catholic missions which aimed to convert and control the native populations, combining with commercial and military interests to disrupt and often destroy traditional native societies.