What would happen if the volcano in Yellowstone erupted?

The Yellowstone supervolcano is different from a regular volcano. Residing underneath Yellowstone, the supervolcano generates enormous amounts of heat near the surface of the ground that in turn powers the thousands of geysers, hot pools, mud pots and steam vents in the park. Geological studies indicate that over the course of recent millions of years the supervolcano has erupted approximately every 600,000 years. There are no indications it will erupt anytime soon. Humanity may have disappeared from planet earth by the time Yellowstone’s supervolcano again erupts. But should that not be the case, and if the land mass of the United States (or whatever it may be called by that time) is roughly the same as now, the eruption could cause various levels of devastation and damage over perhaps one-half of the land mass, while potentially triggering global climate change.