The caldera, which was featured in Roland Emmerich’s (fictional) 2012, has been a fear in recent years due to recent discoveries about the nature of the Yellowstone area. It was revealed to be a supervolcano that had erupted as recently as 70,000 years ago and could erupt again, possibly soon.
The issue with Emmerich’s interpretation is that a Yellowstone eruption wouldn’t be that dramatic: hotspot volcanoes are usually very passive, just spewing out lava from vents, slowly covering the earth around the volcano. A familiar example of a hotspot volcano is Kilauea in Hawaii. It has erupted nearly constantly since 1983, slowly expanding the big island of Hawaii as the Pacific plate moves over the hotspot.
Yellowstone, I believe, would erupt much like this, but on a much larger scale. This, however, is not very good fare for an Emmerich movie (or any action movie for that matter), but may work for an Asimovian short story. What if the Yellowstone caldera erupted and began to cover the entirety of North America, or for that matter, the whole Earth? How would humanity cope, or try to cope?