This does seem to be what may have happened 17 mya when an impactor struck SE Oregon causing the volcanism that created the Snake River and Columbia Basalts and the hot spot that has now migrated to under Yellowstone Park.
Coming in a bit late, but do you have a source for this? It sounds fascinating.
Though I'm still sad that any discovery of such a large impact site means "my" impact crater drops a spot in the world size ranking. ;)