The power of belief
The last big volcano eruption literally plunged the world into a mini ice age, causing both global and local famine . We have documented first hand accounts of both it's ash and vibrations being felt 2 continents away. Would have been more apocalyptic if it wasn't on an island. And Tambora wasn't even a super volcano just an extremely destructive one.
But we have one of these super volcano monsters that is several times more destructive than the 1816 eruption right in the center of our country and it's been overdue to erupt for the last 100 years.
There is no universe where America keeps existing after Yellowstone explodes breh. Canada and Mexico will get strays too because the ash plumes respect no borders.