Based on the information provided in the passage, the two historical events discussed in the video that show the effects of a large oil spill are:
1. The 2010 Deepwater Horizon incident in the Gulf of Mexico, which was one of the worst environmental disasters in U.S. history. The passage states that in this incident, "oil leaked unchecked into the Gulf of Mexico for months."
2. A potential similar or even smaller oil spill event in the desolate Alaska region, which the passage states "could result in incalculable damage."
The passage highlights these two events to illustrate the serious environmental consequences that can arise from oil spills, especially in sensitive and remote regions like Alaska, which the passage describes as a "pristine Alaskan wilderness."