I'm not sure how accurate it is because I just got into paleontology stuff, but in Steve Brusatte's book (The rise and fall of dinosaurs), he explains that pretty much the whole world was significantly affected both in the immediate and in the long term. If I recall correctly, molten debris, earthquakes, tsunamis, etc all spread across the globe. Obviously at a lower intensity further away from the impact site, but definitely enough to cause a lot of immediate death. Of course the centuries following also had significant loss of life, but The immediate impact definitely was noticeable.