Denver will hear the explosion be covered in three feet of ash or so and it will kill everything east and some west of the Rocky Mountains clear east to Ohio or so. Decimate farming and food growing in the Midwest. Throwing half the world into starvation from lack of US food and money. Best place to be is on the lookout at lower or upper Falls in Yellowstone. No suffering that way. Any survivors are in for a treat. IMO
It’ll be hard to breath prior to the ash fall due to the heat from the initial ejection of super heated material. Lets hope it’s delayed a few hundred years.